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Effect of a ban on carrying firearms on homicide rates in 2 Colombian cities


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Homicide is a leading cause of death in Colombia, with much of the fatal interpersonal violence concentrated in the country's largest cities. Firearms are involved in as much as 80% of homicides in Colombia. To evaluate the effect of an intermittent police-enforced ban on carrying firearms on the incidence of homicide in urban Colombia. Interrupted time-series study with multiple replications. Cali, Colombia, during 1993 and 1994 and Bogotá, Colombia, from 1995 through August 1997. The populations of Cali and Bogotá. Carrying of firearms was banned on weekends after paydays, on holidays, and on election days. Enforcement included establishment of police checkpoints and searching of individuals during traffic stops and other routine law enforcement activity. Homicide rates during intervention days were compared with rates during similar days without the intervention; estimates were based on comparisons within the same month, day of week, and time of day. There were 4078 homicides in Cali during 1993 and 1994 (114.6 per 100,000 person-years). In Bogotá, 9106 homicides occurred from 1995 through August 1997 (61 per 100,000 person-years). The incidence of homicide was lower during periods when the firearm-carrying ban was in effect compared with other periods (multivariate-adjusted rate ratio, 0.86 [95% confidence interval [CI], 0.76-0.97] for Cali, and 0.87 [95% CI, 0.77-0.98] for Bogotá). An intermittent citywide ban on the carrying of firearms in 2 Colombian cities was associated with a reduction in homicide rates for both cities.
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. 2000;283(9):1205-1209 (doi:10.1001/jama.283.9.1205) JAMA
Andrés Villaveces; Peter Cummings; Victoria E. Espitia; et al.
in 2 Colombian Cities
Effect of a Ban on Carrying Firearms on Homicide Rates
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Effect of a Ban on Carrying Firearms on
Homicide Rates in 2 Colombian Cities
Andre´s Villaveces, MD, MPH
Peter Cummings, MD, MPH
Victoria E. Espitia, MSc
Thomas D. Koepsell, MD, MPH
Barbara McKnight, PhD
Arthur L. Kellermann, MD, MPH
bean, an estimated 102 000 homi-
cides occurred in 1990 (46.0 per
100 000 person-years).
From 1983 to
1993, the annual rate of homicide in
Colombia increased 366%, from 24 to
88 per 100 000.
In contrast, the crude
homicide rate in the United States in
1993 was 9.5 per 100 000.
Two thirds
of all deaths of Colombian men aged 15
to 44 years were due to homicide in
Much of the recent increase in
fatal interpersonal violence in Colom-
bia has been concentrated in the coun-
try’s 3 largest cities, Bogota´, Medellı´n,
and Cali. These cities contain 23% of
the country’s population and account
for nearly 31% of its homicides.
1994, the rate of homicide in the city
of Cali was 124 per 100 000 person-
; in Bogota´, it was 68 per 100 000
In 1993, firearms were involved in
80% of homicides in Colombia
pared with 70% of homicides in the
United States in the same year.
lombian laws allow individuals to carry
firearms only after an individual per-
mit has been issued by the military
forces; the army has exclusive control
over firearm sales and issues gun per-
mits only to buyers who can offer a con-
vincing justification for ownership and
only after the buyer passes a back-
ground check for past illegal activity.
Individuals with a permit are allowed
to carry concealed firearms anywhere
and at any time, with the exception of
in government buildings and some pri-
vate buildings where posted. In prac-
tice, widespread smuggling has made
it difficult to enforce these laws.
In 1993, the mayor of Cali estab-
lished the Programa para el Desar-
rollo, la Seguridad y la Paz (Program for
Development, Security, and Peace),
known as DESEPAZ, in an effort to stem
the city’s rising rate of homicide.
jectives of the program included the
strengthening of democratic institu-
tions, community empowerment, pri-
ority needs assessment, and a commu-
nication strategy for promotion of
peaceful conflict resolution.
To moni-
tor patterns and trends in homicide
Author Affiliations: Departments of Epidemiology (Drs
Villaveces, Cummings, and Koepsell), Health Ser-
vices (Dr Koepsell), and Biostatistics (Dr McKnight),
School of Public Health and Community Medicine, and
the Harborview Injury Prevention and Research Cen-
ter (Drs Villaveces, Cummings, and Koepsell), Univer-
sity of Washington, Seattle; Department of Interna-
tional Health, Rollins School of Public Health (Dr
Villaveces) and the Emory Center for Injury Control
(Dr Kellermann), Emory University, Atlanta, Ga; and
Programa DESEPAZ, Epidemiologı´a de la Violencia, Al-
caldı´a Municipal de Cali, Universidad del Valle, Cali,
Colombia (Ms Espitia).
Corresponding Author and Reprints: Andre´ s Vil-
laveces, MD, MPH, Harborview Injury Prevention and
Research Center, Box 359960, 325 Ninth Ave, Seattle,
WA 98104-2499 (e-mail:
Section Editor: Annette Flanagin, RN, MA, Manag-
ing Senior Editor.
For editorial comment see p 1193.
Context Homicide is a leading cause of death in Colombia, with much of the fatal
interpersonal violence concentrated in the country’s largest cities. Firearms are in-
volved in as much as 80% of homicides in Colombia.
Objective To evaluate the effect of an intermittent police-enforced ban on carrying
firearms on the incidence of homicide in urban Colombia.
Design Interrupted time-series study with multiple replications.
Setting Cali, Colombia, during 1993 and 1994 and Bogota´ , Colombia, from 1995
through August 1997.
Participants The populations of Cali and Bogota´.
Intervention Carrying of firearms was banned on weekends after paydays, on holi-
days, and on election days. Enforcement included establishment of police checkpoints
and searching of individuals during traffic stops and other routine law enforcement
Main Outcome Measure Homicide rates during intervention days were com-
pared with rates during similar days without the intervention; estimates were based
on comparisons within the same month, day of week, and time of day.
Results There were 4078 homicides in Cali during 1993 and 1994 (114.6 per 100 000
person-years). In Bogota´ , 9106 homicides occurred from 1995 through August 1997
(61 per 100 000 person-years). The incidence of homicide was lower during periods
when the firearm-carrying ban was in effect compared with other periods (multivariate-
adjusted rate ratio, 0.86 [95% confidence interval {CI}, 0.76-0.97] for Cali, and 0.87
[95% CI, 0.77-0.98] for Bogota´).
Conclusion An intermittent citywide ban on the carrying of firearms in 2 Colom-
bian cities was associated with a reduction in homicide rates for both cities.
JAMA. 2000;283:1205-1209
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more closely, a fatal injury surveil-
lance system was established. A de-
tailed description of this system can be
found elsewhere.
These programs were
later copied in Bogota´ and a similar sur-
veillance system was created in 1995.
In an effort to reduce the incidence
of homicide, the mayors and the met-
ropolitan police commanders of both
cities decided to ban carrying firearms
on weekends after a payday, on holi-
days, and on election days. These pe-
riods are historically associated with
higher rates of homicide.
We sought to determine whether a
ban on carrying firearms was associ-
ated with any change in the incidence
of homicide.
Study Sites and Periods
Cali (population, 1 803 662 in 1994) is
the third largest city in Colombia, and
Bogota´ (population, 5 639 328 in 1996)
is the largest city and the nation’s capi-
tal. Both are major cultural, indus-
trial, and agricultural centers.
In Cali, the study took place from the
beginning of 1993 through the end of
1994. In Bogota´, the study took place
from the beginning of 1995 through Au-
gust 1997. During these times, a spe-
cial injury surveillance system col-
lected data on all homicides. In addition,
all elements of the DESEPAZ program,
aside from the ban on carrying fire-
arms, were continuously in effect.
The Intervention
Intervention strategies were imple-
mented through a coordinated effort by
the metropolitan police and the may-
ors’ offices. By special decree, citizens
(including those with permits to carry
firearms) were forbidden to carry their
firearms during periods that were ex-
pected to have higher rates of homi-
cide, based on past experience. These
periods included weekends after semi-
monthly paydays, holidays, any week-
end that adjoined a holiday, and elec-
tion days. However, because of the effort
involved, the intervention was applied
to only some of the eligible periods. In
addition, it was applied to some
weekends that did not come after pay-
days or adjoin a holiday.
The public was notified about the ban
through the media. Television, news-
papers, and radio were used to dissemi-
nate this information and the pro-
grams reached national attention,
making it unlikely that individuals were
uninformed about its application times.
The ban made reference only to fire-
arms, not to other weapons. In some
cases, police confiscated knives or other
weapons because the presence of these
other weapons was thought to be dan-
gerous (eg, an individual who was in a
The intervention took effect at 6
on the day before the designated pe-
riod began and ended at 6
AM on the
day after the last day of the period.
Thus, a typical weekend intervention
began at 6
PM on Friday and ended at
AM on the subsequent Monday. In
Cali, the intervention was applied on
34 occasions for a total of 89 days; the
intervention was first applied in No-
vember 1993 and was applied inter-
mittently during 1994. In Bogota´, the
intervention was applied on 22 occa-
sions for a total of 67 days during 3
intervals: December 1995 through
March 1996, December 1996 through
February 1997, and March and April
During intervention days, police es-
tablished checkpoints throughout the
city and, at their discretion, searched
individuals. Searches for weapons were
also conducted during traffic stops and
other law enforcement activities. Lo-
cations for checkpoints were selected
by each local police commander and
were usually in areas where police be-
lieved criminal activities were com-
mon. Police also searched individuals
by going into bars and clubs and search-
ing patrons. During the ban, police
policy directed that if a legally ac-
quired firearm was found on an indi-
vidual, the weapon was to be tempo-
rarily taken from the individual and the
individual fined. Individuals without
proof of legally acquiring the firearm
were to be arrested and the firearm per-
manently confiscated.
Study Data
A homicide was defined as any inten-
tional killing of 1 person by another,
regardless of method. The DESEPAZ
program in Cali and the program in
Bogota´ collected data on a weekly ba-
sis from the National Institute of Le-
gal Medicine and Forensic Sciences, the
metropolitan police, the district attor-
ney’s office, and the Department of
Transportation. A committee of repre-
sentatives from each of these organi-
zations met once per week to review
cases and share information. All of these
activities were coordinated by an epi-
The fatal injury surveillance system
collected information on victim iden-
tity, place and time of injury, and in-
jury circumstances. The manner of
death (suicide, homicide, or uninten-
tional) and the mechanism of death (eg,
fall, knife, firearm) were determined
from information obtained at the scene
from witnesses and from other infor-
mation provided by the police, transit
police, coroner, hospital, or postmor-
tem examination. In both cities, pa-
thologists of the National Institute of
Legal and Forensic Medicine per-
formed autopsies on all cases of injury-
related death. Data were entered only
after the final medical examiner’s di-
agnosis was obtained. All counts, rates,
and analyses are limited to homicides
of Cali and Bogota´ residents.
Data regarding the time of assault
were missing for 16 (0.4%) of the 4078
homicides in Cali; this proportion was
so small that we simply omitted these
records from analyses that required time
of assault. Data regarding time of as-
sault were missing for 1965 (21.6%) of
the 9106 homicides in Bogota´. We ini-
tially omitted these records from analy-
ses that required time of assault. We
then classified assaults by the age and
sex of the victim and whether the event
occurred on a payday weekend, other
weekend, or weekday; within each stra-
tum formed by these variables, we im-
puted missing values for hour of as-
sault using an approximate Bayesian
bootstrap method.
This imputation
process was carried out 10 times; all
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analyses of Bogota´ data that used im-
puted information were carried out on
each of the 10 imputed data sets and
all estimates, variances, and confi-
dence intervals (CIs) were calculated
using methods suitable for combining
data based on multiple imputa-
The study design was that of an inter-
rupted time series with multiple repli-
cations; the intervention was applied in-
termittently in both cities, allowing us
to compare periods with the interven-
tion with similar periods without the
Counts of deaths and total popula-
tion data were obtained from the Cali
and Bogota´ surveillance databases. The
number of homicides that occurred dur-
ing each hour were categorized by sex,
age (,15, 15-35, or .35 years), and
whether a firearm was used. Rates were
calculated on the basis of person-
years of exposure for Cali in 1993
(1 748 815) and 1994 (1 803 662) and
Bogota´ in 1995 (5 510 040), 1996
(5 639 328), and through the end of Au-
gust 1997 (3 831 624).
We first carried out a stratified analy-
sis using the method of indirect stan-
dardization. The stratification catego-
ries were weekday, payday weekend,
other weekend, time of year grouped
into 4-month intervals, and time of week
grouped into 28 equal intervals of 6
hours each. The stratum-specific rates
on nonintervention days were applied
to the person-time distribution of the in-
tervention days to obtain an expected to-
tal number of deaths.
The observed
number of deaths on intervention days
was then divided by this expected num-
ber to obtain a standardized mortality ra-
tio. Finally, a standardized rate for the
intervention group was calculated as the
product of its crude rate and the stan-
dardized mortality ratio.
To control for potential confound-
ing more completely, incidence rate ra-
tios were estimated using negative bi-
nomial regression to compare periods
with the intervention with all other pe-
riods, controlling for other character-
istics of periods that were potential con-
We divided each week into
28 consecutive 6-hour periods and in-
cluded 27 variables, coded 0 or 1, to ac-
count for variation in homicide inci-
dence among these intervals. Similarly,
we used 11 variables to account for
variation by month of the year. Addi-
tional variables were used to indicate
whether a weekend followed a payday
and whether a day was a holiday or elec-
tion day. To control for any trend in ho-
micide rates over the study period, the
days were assigned consecutive num-
bers. This continuous variable was in-
cluded in the models by using 2 frac-
tional polynomial terms as described by
Royston and Altman.
Categories of
age and sex were also examined as po-
tential confounders.
If a person was planning to assault
someone with a firearm, that person
might decide that it was too risky to carry
a firearm during an intervention period
and delay an assault for a few days to a
period not covered by the intervention.
If this occurred, any apparent reduc-
tion in homicide during intervention pe-
riods might be followed by a compen-
satory increase in homicides shortly after
the intervention. To examine this pos-
sibility, we created a variable for the 7-day
interval immediately following each in-
tervention period, coded 0 or 1, to see if
homicides were more common after the
intervention period.
Because the police intervention fo-
cused on finding and confiscating fire-
arms, we used the same regression
methods to estimate the effect of the in-
tervention on firearm-related and other
homicides. To test whether the asso-
ciation of the intervention with fire-
arm vs nonfirearm homicides was sig-
nificantly different, we repeated the
analysis using multinomial logistic re-
The populations of both cit-
ies during each 6-hour period were
treated as cohorts in which each indi-
vidual could experience 3 possible out-
comes: survival, death by firearm ho-
micide, or death by other homicide. The
same predictor variables were used.
Homicides might be serially corre-
lated over time. To check for any se-
rial correlation, we calculated autocor-
relation coefficients for the deviance
residuals of our final regression mod-
els using lags of 1 to 40 days.
During 1993 and 1994, there were 4078
homicides in Cali (rate, 114.6 per
100 000 person-years) (T
ABLE 1). There
were 9106 homicides in Bogota´ be-
tween 1995 and August 1997 (rate, 61
per 100 000 person-years) (Table 1). In
Cali, the incidence of homicide rose
from 104.9 per 100 000 person-years in
1993 to 124.3 per 100 000 person-
years in 1994, while in Bogota´, homi-
cides declined from 66.2 per 100 000
person-years in 1995 to 51.6 per
100 000 person-years in the first 8
months of 1997. Nearly two thirds of
the victims in both cities were men aged
15 to 34 years; for Cali, the homicide
rate in this group was 417.4 per 100 000
person-years; for Bogota´, it was 207.7
per 100 000 person-years. Seventy-
nine percent (n = 3235) of Cali homi-
cides involved firearms. Seventy-four
percent (n = 6735) of homicides in
Bogota´ were firearm-related. Most other
homicides involved a knife or other cut-
ting instrument.
In Cali, during nonintervention days
in 1993 and 1994, police confiscated
230 firearms (0.8 per day). During in-
tervention days, 307 guns were confis-
cated (4 per day).
Data on firearm con-
fiscation during intervention and
nonintervention days were not avail-
able for Bogota´.
Most of the Cali homicides (n = 3347)
occurred on days when there was
no intervention (107.5 per 100 000
person-years). For Bogota´, an average of
8262 homicides occurred during the
nonintervention periods (59.3 per
100 000 person-years). During days
when the intervention was in effect, there
were 715 homicides in Cali (161.8 per
100 000 person-years) and an average of
844 in Bogota´ (81 per 100 000 person-
years); as expected, the homicide rate was
higher during these weekend and holi-
day periods. We divided periods into 3
categories: weekdays, payday week-
ends, and other weekends. Within each
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of these 3 categories, standardized ho-
micide rates were lower when the inter-
vention was in effect for Cali (T
ABLE 2).
For Bogota´, we found similar results ex-
cept in the category of other weekends
(nonpayday), for which the rate was
slightly higher during intervention pe-
riods (Table 2).
After adjusting in a regression model
for weekend periods, holidays, pay-
days, 6-hour periods within each week,
month of year, and the overall trend in
homicide rates, the incidence of homi-
cide in Cali during periods when the
ban was in effect was significantly lower
than in nonintervention periods (rate
ratio, 0.86; 95% CI, 0.76-0.97). The rate
ratio for Bogota´ using only records with-
out missing data (7141 observations)
was 0.87 (95% CI, 0.76-0.99). The rate
ratio for Bogota´ using these data supple-
mented with observations derived from
10 imputed data sets to account for
missing data (9106 observations) was
0.87 (95% CI, 0.77-0.98).
Further adjustment for slight changes
in the age and sex distribution of the
population over time had no impor-
tant effect on these estimates. In the 7
days following intervention periods, the
incidence of homicide was not substan-
tially different from that during com-
parable nonintervention intervals (for
Cali, rate ratio, 1.03 [95% CI, 0.94-
1.13] for Bogota´, rate ratio, 0.99 [95%
CI, 0.90-1.08]). There was no statisti-
cally significant evidence of serial cor-
relation in our regression models.
Although the ban focused on fire-
arms, we conducted a statistical test of
the difference in the apparent effect of
the program on firearm-related and
other homicides; results were not sig-
nificant (P = .30 for Cali and P = .70 for
Bogota´). Furthermore, the direction of
association was inconsistent between
the 2 cities. In Cali, the intervention was
more strongly associated with nonfire-
arm homicides (rate ratio, 0.77 [95%
CI, 0.61-0.97]) than with firearm ho-
micides (rate ratio, 0.90 [95% CI,
0.79-1.03]). In Bogota´, however, the in-
tervention was more strongly associ-
ated with firearm-related homicides
(rate ratio, 0.85 [95% CI, 0.75-0.97])
Table 1. Numbers and Rates of Homicide by Year, Age, and Sex
Cali, Colombia
Bogota´ , Colombia
No. of
Homicide Rate per
100 000 Person-Years
No. of
Homicide Rate per
100 000 Person-Years
1993 1836 104.9 . . . . . .
1994 2242 124.3 . . . . . .
1995 . . . . . . 3645 66.2
1996 . . . . . . 3484 61.7
1997† . . . . . . 1977 51.6
Female 274 14.5 625 7.9
Male 3804 228.5 8481 119.8
Age, y
0-14 57 5.0 172 3.9
15-34 2825 196.1 6085 101.4
$35 1196 121.7 2849 63.0
Female, age, y
0-14 17 1.9 34 1.5
15-34 172 21.3 357 11.0
$35 85 16.2 234 9.6
Male, age, y
0-14 40 7.0 138 6.2
15-34 2653 417.4 5728 207.7
$35 1111 242.3 2615 126.0
Ellipses indicate not applicable.
†Data are through August 31, 1997.
Table 2. Numbers, Rates, and Standardized Mortality Ratios for Homicides During
Intervention and Nonintervention Periods
No. of
Crude Homicide
Rate per 100 000
Mortality Ratio
(95% Confidence
Cali, Colombia, 1993-1994
Intervention 715 161.8 89.0 0.83 (0.77-0.89)
Nonintervention 3347 107.5 107.5 Reference
Intervention 26 87.6 79.5 0.94 (0.61-1.38)
Nonintervention 1908 84.6 84.6 Reference
Payday weekends
Intervention 468 162.1 139.1 0.82 (0.75-0.90)
Nonintervention 585 169.6 169.6 Reference
Nonpayday weekends
Intervention 221 178.8 141.7 0.86 (0.75-0.98)
Nonintervention 854 165.8 165.8 Reference
Bogota´ , Colombia, 1995-1997‡
Intervention 844.3 81.3 54.2 0.92 (0.86-0.97)
Nonintervention 8261.7 59.3 59.3 Reference
Intervention 46 38.3 40.6 0.96 (0.70-1.28)
Nonintervention 4011.9 42.2 42.2 Reference
Payday weekends
Intervention 303.9 82.0 79.4 0.78 (0.70-0.87)
Nonintervention 1861.9 101.8 101.8 Reference
Nonpayday weekends
Intervention 494.4 90.2 93.4 1.02 (0.94-1.12)
Nonintervention 2387.9 91.4 91.4 Reference
Rates were standardized to the unexposed population using indirect standardization methods.
†Weekday intervention periods were holidays that did not fall on a weekend.
‡Numbers and rates for Bogota´ are based on data from 10 imputations of hour of death (1965 observations imputed).
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at University Of North Carolina - Chapel Hill on July 12, 2010 www.jama.comDownloaded from
than with other homicides (rate ratio,
0.88 [95% CI, 0.72-1.06]).
During 1993 and 1994, an aggressive
program of banning and confiscating
firearms from residents was intermit-
tently applied in Cali. A similar pro-
gram was replicated in Bogota´ from
1995 through 1997. In Cali, we found
that the rate of homicide was 14% lower
(95% CI, 3%-24%) than expected dur-
ing periods when the ban on carrying
firearms was in effect. In Bogota´, the in-
cidence was 13% lower (95% CI, 1%-
24%) during intervention periods.
Whenever an exposure such as a law
or police activity is applied to an en-
tire population, the possibility exists
that any apparent effect on outcomes
could be due to other temporal changes
that were not accounted for in the
analysis. Our study, however, is un-
usual in that the intervention was ap-
plied intermittently. This provided an
opportunity to separate the interven-
tion effect from the overall change in
homicide rates. Whatever additional
factors might have affected homicide
rates in these cities during the study
intervals, it seems unlikely that they
would have reduced homicides selec-
tively during periods when the police
intervention was in effect.
Another study has suggested that
confiscation of illegally carried fire-
arms may reduce violent crime.
1994, a special unit of the Kansas City,
Mo, police department targeted illegal
gun carrying in a neighborhood with
high rates of firearm violence. During
the intervention period, firearm-
related crimes declined 49% in the in-
tervention neighborhood; no reduc-
tion was noted in a similar control
neighborhood that did not receive the
intervention. While the measured re-
duction in crime may have been due to
the intervention program, very few
weapons were seized.
In both Cali and Bogota´, the ban on
carrying firearms was applied to crimi-
nals and law-abiding citizens alike. Even
individuals who were normally autho-
rized to carry a firearm could not le-
gally do so on days when the decree was
in effect. Although a population-wide
approach of this sort may disarm more
law-abiding citizens than criminals, it
appears to have been associated with a
beneficial effect on homicide rates.
Although it appears that the interven-
tion in both cities prevented some ho-
micides, the mechanism for this ben-
efit is not clear. The program might have
prevented violence by incarcerating per-
sons who violated the firearms ban or
it might have deterred some people from
carrying a concealed weapon or even ap-
pearing in public during the interven-
tion. Although the program was specifi-
cally directed at firearms, we found that
the effect was not confined to firearm-
related homicides. This suggests that the
program may have worked in part by
promoting a visible and aggressive po-
lice presence, which discouraged or in-
terrupted episodes of serious interper-
sonal violence.
A program of this type may not have
a similar effect in cities where homi-
cide is less common. Furthermore, con-
stitutional restrictions on police search
procedures would prevent transferring
the methods used in Cali and Bogota´to
any city in the United States. Our study
suggests that police programs such as
those applied in Cali and Bogota´ can sup-
press serious interpersonal violence and
save lives. This kind of program may be
suitable for regions of the world where
homicide rates are very high and pro-
grams of this type are permissible.
Funding/Support: This study was supported in part
by an education grant from the Japan–Inter-
American Development Bank Scholarship Program and
a grant from the Instituto Colombiano para el Desar-
rollo de la Ciencia y la Tecnologı´a Francisco Jose´de
Caldas “Colciencias.” The data sets used for this analy-
sis were provided by the DESEPAZ Program Office of
Epidemiology of Violence from the Office of the Mayor
of Cali, the National Institute of Legal Medicine and
Forensic Sciences, and the Office of the Mayor of San-
tafe´ de Bogota´.
Acknowledgment: We are indebted to Rodrigo Guer-
rero, MD, DrPH, mayor of Cali from 1992-1994. We
also thank Gloria Sua´ rez, MD, National Institute of Le-
gal Medicine and Forensic Sciences, and Hugo Acero
Vela´ zquez, security advisor for Bogota´ during 1996-
1997, both of whom provided most of the informa-
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... Antes de 2016, la restricción al porte de armas en Colombia era una medida empleada de manera temporal a nivel local con el propósito de preservar el orden público alrededor de coyunturas específicas (Villaveces et al., 2000). Esta medida demostró ser efectiva en la reducción de las lesiones por armas de fuego en el país (Villa y Restrepo, 2010). ...
... Un estudio previo que evalúa las restricciones temporales al porte de armas de fuego muestra que, en promedio, la restricción está asociada a la reducción de un homicidio por arma de fuego por cada cuatro días de implementación (Villa y Restrepo, 2010). La restricción al porte de armas en Bogotá y Cali, durante casi 20 % de los días del año en la década de los noventa, demostró reducir la tasa de homicidios entre 13 % y 14 % (Villaveces et al., 2000). Esta evidencia al nivel local sugiere que la restricción al porte de armas a nivel nacional constituye una herramienta efectiva para reducir los homicidios por arma de fuego, potencialmente con mayores efectos al evitar conflictos jurisdiccionales. ...
... Esto está probablemente relacionado a factores de violencia contemporáneos a la restricción, como la reconfiguración de grupos armados, la pobre implementación de los acuerdos de paz y el incremento de los cultivos de coca (Cousins, 2019; Fundación Ideas para la Paz, 2019; Medicina Legal y Ciencias Forenses, 2018). Dado que la evidencia a nivel local sugiere que la restricción al porte de armas reduce los homicidios con armas de fuego (Villaveces et al., 2000;Villa y Restrepo, 2010;WHO, 2009; Vecino-Ortiz, AI, Guzmán-Tordecillas, n.d.), es posible que en el escenario contrafactual en el que la restricción no existiera, el incremento en los homicidios hubiese sido mayor. ...
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Colombia es uno de los países con más muertes por armas de fuego en el mundo después de Brasil, Estados Unidos, India y México; 82 % de esas muertes tienen lugar en entornos urbanos y no están relacionadas con el conflicto armado (Naghavi et al., 2018). Las lesiones por este tipo de armas causaron más de 520.000 muertes en el país desde 1990, equivalente a 10 % de todas las muertes ocurridas y 15 % de todos los años de vida perdidos prematuramente (Institute for Health Metrics and Evaluation, 2018). 90 % de las muertes por armas de fuego ocurren durante los años productivos de la vida y se dan principalmente en hombres jóvenes en contextos vulnerables (Instituto Nacional de Salud, 2014; Instituto Nacional de Salud, 2017; Naghavi et al., 2018; Instituto Nacional de Medicina Legal y Ciencias Forenses, 2016). Ante esta realidad, las entidades del nivel nacional y local se han enfocado en implementar intervenciones que reduzcan la violencia y, en particular, las lesiones por arma de fuego. La presente Nota de Política expone las conclusiones de la revisión normativa sobre la restricción al porte de armas en Colombia y hace una revisión de la evidencia que concierne a dicha política. Dicha revisión rastrea los principios legales que antecedieron a la restricción nacional al porte de armas realizada en 2016 y sus renovaciones posteriores, y es parte de los resultados de un estudio que busca entender el proceso de toma de decisiones y el rol de la sociedad civil que llevó a la implementación de la restricción, así como su adopción en poblaciones jóvenes en contextos vulnerables.
... No caso de homicídios em locais de trabalho, as principais vítimas são os homens, trabalhadores autônomos, especialmente taxistas (Moracco et al., 2000), e profissionais da área de segurança. Embora a arma de fogo seja o principal meio pelo qual se perpetram os homicídios, é estranho que apenas dois artigos proponham a limitação ou proibição do porte desses instrumentos como medida de prevenção para o homicídio (Hemenway & Miller, 2000;Villaveces et al., 2000). Este último autor analisa a realidade de duas cidades colombianas. ...
Apresenta um panorama atualizado sobre o impacto da violência na saúde pública. Examinam-se as tendências das produções científicas sobre o assunto e busca-se conceituar o tema em seus aspectos filosóficos, teóricos, sociais e culturais. Analisam-se também a mortalidade por causas externas no Brasil, a morbidade por envenenamento e as diferentes formas de violência, assim como a relação entre drogas e violência e entre mídia e violência. Obra que traz contribuição tanto para os envolvidos com a saúde coletiva, a sociologia, a antropologia e a segurança pública como para os formuladores e gestores das políticas públicas.
... Hasta donde sabemos, las únicas políticas de control de armas que han sido objeto de evaluaciones de impacto son la prohibición del porte de armas en las ciudades colombianas de Bogotá y Cali (Villaveces et al. 2000) y la política brasileña conocida como el Estatuto del Desarme (Brazil, MS/SVS/CGIAE 2007;de Souza et al. 2007). Las mismas limitaciones metodológicas que di cultan la evaluación de teorías causales hacen que resulte extremada- mente difícil obtener evidencia concluyente sobre el impacto de las políticas de control de armas. ...
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Resumen El artículo presenta una visión general y actualizada de las políticas de control de armas pe-queñas en América Latina. Con el n de encontrar un equilibrio entre su uso legítimo y la prevención de daños sociales, todos los Estados latinoamericanos regulan la posesión y el uso de armas de fuego. El análisis comparativo demuestra que existe una gran heterogeneidad entre los países, pero la mayoría lo hace de formas relativamente restrictivas y con sistemas rigurosos de licencia y registro. A pesar de ello, el acatamiento limitado de las leyes y la falta de evidencia empírica sobre sus impactos di cultan la evaluación de sus resultados. En de nitiva, no es posible determinar si estas políticas previenen lesiones y muertes, en consonancia con un área de políticas públicas en la cual persisten demasiadas incógnitas. Palabras clave: América Latina; armas de fuego; armas pequeñas; control de armas; políticas de armas; regulación de armas Abstract is article provides a general and updated overview of small arms control policies in Latin Amer-ica. In order to strike a balance between their legitimate use and the prevention of social harm, all Latin American states regulate the possession and use of rearms. A comparative analysis shows that there is a wide heterogeneity between countries, but most do so in relatively restrictive ways and with rigorous licensing and registration systems. Nevertheless, limited compliance with the law and the lack of empirical evidence on their impact make it di cult to evaluate their results. Ultimately, it is not possible to determine whether these policies prevent injuries and deaths, in line with an area of public policy in which important evidence is still missing.
... 47 Several other countries have shown that firearm-related injury and death are largely preventable and that policy change can have considerable impact. [48][49][50][51][52][53][54] Although media attention focuses largely on firearm violence in urban centres, our findings highlight that men in rural Ontario are at high risk for death from firearm-related injuries secondary to self-harm. Different injuryprevention strategies may be needed to address specific at-risk groups in different settings. ...
Background: Firearm-related injury is an important and preventable cause of death and disability. We describe the burden, baseline characteristics and regional rates of firearm-related injury and death in Ontario. Methods: We conducted a population-based cross-sectional study using linked data from health administrative data sets held at ICES. We identified residents of Ontario of all ages who were injured or died as a result of a firearm discharge between Apr. 1, 2002, and Dec. 31, 2016. We included injuries classified as assault, unintentional, self-harm or undetermined intent secondary to handguns, rifles, shotguns and larger firearms. The primary outcome was the incidence of nonfatal and fatal injuries resulting in an emergency department visit, hospital admission or death. We also describe regional and temporal rates. Results: We identified 6483 firearm-related injuries (annualized injury rate 3.54 per 100 000 population), of which 2723 (42.3%) were fatal. Assault accounted for 40.2% (1494/3715) of nonfatal injuries and 25.5% (694/2723) of deaths. Young men, predominantly in urban neighbourhoods, within the lowest income quintile were overrepresented in this group. Injuries secondary to self-harm accounted for 68.0% (1366/2009) of injuries and occurred predominantly in older men living in rural Ontario across all income quintiles. The case fatality rate of injuries secondary to self-harm was 91.7%. Self-harm accounted for 1842 deaths (67.6%). Interpretation: We found that young urban men were most likely to be injured in firearm-related assaults and that more than two-thirds of self-harm-related injuries occurred in older rural-dwelling men, most of whom died from their injuries. This highlights a need for suicide-prevention strategies in rural areas targeted at men aged 45 or older.
... Federation units with higher rates of firearm collection decreased their rates (São Paulo, Rio de Janeiro, Distrito Federal, others), while federation units with lower rates of firearm collection experienced an increase in firearm homicide rates. Similarly, positive outcomes have been observed in countries that applied regulatory measures for the use of firearms, such as Australia [1,2,14], South Africa [15], and Colombia [24,25]. Japan, which banned the possession of firearms and rifles in 1945, stands out as having one of the lowest firearm homicide rates in the world, at 0.03 per 100,000 inhabitants [1]. ...
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Background Brazil leads the world in number of firearm deaths and ranks sixth by country in rate of firearm deaths per 100,000 people. This study aims to analyze trends in and burden of mortality by firearms, according to age and sex, for Brazil, and the association between these deaths and indicators of possession and carrying of weapons using data from the global burden of diseases, injuries, and risk factors study (GBD) 2017. Methods We used GBD 2017 estimates of mortality due to physical violence and self-harm from firearms for Brazil to analyze the association between deaths by firearms and explanatory variables. Results Deaths from firearms increased in Brazil from 25,819 in 1990 to 48,493 in 2017. Firearm mortality rates were higher among men and in the 20–24 age group; the rate was 20 times higher than for women in the same age group. Homicide rates increased during the study period, while mortality rates for suicides and accidental deaths decreased. The group of Brazilian federation units with the highest firearm collection rate (median = 7.5) showed reductions in the rate of total violent deaths by firearms. In contrast, the group with the lowest firearm collection rate (median = 2.0) showed an increase in firearm deaths from 2000 to 2017. An increase in the rate of voluntary return of firearms was associated with a reduction in mortality rates of unintentional firearm deaths ( r = −0.364, p < 0.001). An increase in socio-demographic index (SDI) was associated with a reduction in all firearm death rates ( r = −0.266, p = 0.008). An increase in the composite index of firearms seized or collected was associated with a reduction in rates of deaths by firearm in the subgroup of females, children, and the elderly ( r = −0.269, p = 0.005). Conclusions There was a change in the trend of firearms deaths after the beginning of the collection of weapons in 2004. Federation units that collected more guns have reduced rates of violent firearm deaths.
... It is worth noting that, although rates in Colombia remain high, from 1990 to 2017 DALYs declined by 61.7%, in part due to militaristic and social economic policies aimed at ending armed conflict and eradicating drug trafficking (31) which resulted, in 2016, in the end of a 53 year-long civil war through a peace agreement between the Colombian Government and the Revolutionary Armed Forces of Colombia (FARC). Other notable initiatives include banning of carry permits for guns, which started out as a time and occasion specific ban in major cities in the early 1990s, and a general ban in the capital, Bogotá, in 2012 and became nationwide in 2015 (32)(33)(34). Furthermore, given the complexity of the relationship between police, crime and communities in Columbia, addressing interpersonal violence through means such as alcohol regulation, which was associated with a lower risk of homicide in the city of Cali, may be an effective intervention (35). ...
... A recent systematic review of 130 studies across 10 countries found that reductions in firearm deaths were associated with the simultaneous implementation of laws encompassing multiple firearm restrictions, and SA was mentioned as a key example alongside the USA, Canada, Australia, New Zealand (NZ) and Brazil. [47] Several studies have shown significant decreases following access restrictions through including one study each from NZ, [48] Brazil, [49] Austria [50] and Colombia, [51] and two from the USA. [52,53] In Australia, studies have attributed the decline in firearm homicide and suicide to the 1996 National Firearms Agreement designed to prevent mass shootings. ...
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Injuries impose a fourth major disease burden on the South African population, which is driven in particular by the high incidence of interpersonal violence. There was a significant decline in mortality from interpersonal violence between 1997 and 2012, and research conducted by South African Medical Research Council (SAMRC) researchers has ascribed much of this decline to a decrease in firearm homicide. In the present brief review, we summarise South African research on fatal and non-fatal firearm injuries, with a particular focus on research conducted by SAMRC intra- and extramural units between 1969 and 2019. More recent data suggest a lapse in firearm control that has led to an increase in homicide and that the fluctuating homicide rate is being influenced by adherence to firearm control policies.
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This Campbell systematic review examines the impacts of police strategies to reduce illegal possession and carrying of firearms on gun crime. Examples include gun detection patrols in high‐crime areas, enhanced surveillance of probationers and parolees, weapon reporting hotlines, consent searches, and other similar tactics. Four studies met the inclusion criteria, reporting a total of seven non‐randomized tests of directed patrols focused on gun carrying in three American cities (five tests) and two Colombian cities (two tests). These studies suggest that directed patrols focused on illegal gun carrying prevent gun crimes. However, conclusions and generalizations must be qualified based on the small number of studies, variability in study design and analytic strategy across the studies, pre‐intervention differences between intervention and comparison areas, and limited data regarding factors such as implementation, crime displacement, and long‐term impact. There is also a strong need for rigorous study of other strategies to reduce illegal possession and carrying of firearms. Executive summary/Abstract BACKGROUND Criminal misuse of firearms is among the world's most serious crime problems. Strategies to reduce gun violence include efforts to restrict the manufacture and sale of firearms, interrupt the illegal supply of guns, deter gun possession, reduce gun carrying in public places, toughen responses to illegal gun use, reduce demand for firearms, promote responsible ownership of guns, and address community conditions that foster gun crime. In this review, we examine research on the effectiveness of selected law enforcement strategies for reducing gun crime and gun violence. OBJECTIVES This review examines the impacts of police strategies to reduce illegal possession and carrying of firearms on gun crime. Examples include gun detection patrols in high‐crime areas, enhanced surveillance of probationers and parolees, weapon reporting hotlines, consent searches, and other similar tactics. CRITERIA FOR INCLUSION OF STUDIES Studies using randomized designs or quasi‐experimental designs involving a nonintervention condition were eligible for inclusion. Eligible studies had to include pre and post‐intervention measurements of the outcome measure(s) for an intervention area(s) or group(s) and at least one comparison area or group without the intervention. However, we also included studies involving repeated interventions with one group or area in which the intervention and comparison units consisted of samples of time with and without the intervention. Eligible studies also had to measure gun‐related crime (e.g., gun murders, shootings, gun robberies, gun assaults). The review does not include studies in which eligible interventions were implemented simultaneously with other new crime‐reduction efforts. SEARCH STRATEGY We searched 11 national and international databases for published and unpublished literature available through the end of 2009; examined 25 reviews and compilations of research on policing, gun control, and violence reduction; and searched the websites of five prominent police and criminal justice organizations in the United States and the United Kingdom. Four studies met the inclusion criteria, reporting a total of 7 non‐randomized tests of directed patrols focused on gun carrying in three American cities (5 tests) and two Colombian cities (2 tests). DATA COLLECTION AND ANALYSIS From each included study, we extracted data pertaining to research design, subject characteristics, intervention(s), and outcome measure(s). We present a detailed narrative assessment of each included study, followed by a qualitative and quantitative synthesis of key features and results across studies. Our synthesis does not include a statistical meta‐analysis of the results due to variability in the study designs and problems in computing a usable standardized effect size index for the studies. MAIN RESULTS Six of the seven tests (not all of which were independent) suggest that directed patrols reduced gun crime in high‐crime places at high‐risk times. The Colombian studies, which were based on before and after changes from repeated interventions measured at the city level, estimated that crackdowns on gun carrying reduced firearm homicides 10% to 15%. Estimated effects were generally larger and more variable in the American studies, which examined before and after changes in smaller target areas (beats or patrol zones) relative to changes in comparison areas. With one exception, the American studies found that gun crime declined by 29% to 71%, depending on the outcome measures and statistical techniques used. Authors' Conclusions: These studies suggest that directed patrols focused on illegal gun carrying prevent gun crimes. However, conclusions and generalizations must be qualified based on the small number of studies, variability in study design and analytic strategy across the studies, pre‐intervention differences between intervention and comparison areas, and limited data regarding factors such as implementation, crime displacement, and long‐term impact. There is also a strong need for rigorous study of other strategies to reduce illegal possession and carrying of firearms.
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Overall, teachers' multi‐component classroom management programmes have a significant positive effect in decreasing aggressive or problematic behaviour in the classroom. Students in the treatment classrooms in all 12 studies reviewed showed less disruptive or problematic behaviours when compared to the students in control classrooms without the intervention. It is not possible to make any conclusions regarding what components of the management programmes are most effective due to small sample size and lack of information reported in the studies reviewed. STRUCTURED ABSTRACT Background One of the most common criticisms of spatially focused policing efforts (such as Problem‐Oriented Policing, police ‘crackdowns’ or hotspots policing) is that crime will simply relocate to other times and places since the “root causes” of crime were not addressed. This phenomenon—called crime displacement—has important implications for many policing projects. By far, spatial displacement (movement of crime from a treatment area to an area nearby) is the form most commonly recognized. At the extreme, widespread displacement stands to undermine the effects of geographically focused policing actions. More often, however, research suggests that crime displacement is rarely total. On the other end of the displacement continuum is the phenomenon of ‘diffusion of crime control benefits’ (a term coined by Ron Clarke and David Weisburd in 1994). Diffusion occurs when reductions of crime (or other improvements) are achieved in areas that are close to crime prevention interventions, even though those areas were not actually targeted by the intervention itself. Objectives To synthesize the evidence concerning the degree to which geographically focused policing initiatives are related to spatial displacement of crime or diffusion of the crime control benefits. Search Strategy A number of search strategies were used to retrieve relevant studies. First, we undertook a keyword search of electronic abstract databases. Second, we searched bibliographies of existing displacement reviews and reviews of the effectiveness of focused policing initiatives. Third, we did forward searches for works that had cited key displacement publications. Fourth, we reviewed research reports of professional research and policing organizations. Fifth, we undertook a hand search of pertinent journals and publications. Finally, once these searches were all completed we emailed a list of the studies that we had assessed as meeting (and a separate list of those not meeting) our criteria to a number of key scholars with knowledge of the area to identify any further studies we might have missed. Selection Criteria Eligible studies met the following criteria; (1) they evaluated a policing initiative; (2) this initiative was geographically focused to a local area; (3) the evaluation included a quantitative measure of crime for both a ‘treatment’ area and a displacement/diffusion ‘catchment’ area. This needed to be available for both a pre‐ and a post‐ (or during‐) intervention period. Other criteria specified that the study was written in English and that it reported original research findings. The studies could have been conducted at any point in time and at any location. Both published and unpublished studies were included. Data Collection and Analysis For all of our 44 eligible studies, we produced a narrative review and a summary of the author's findings, concerning the effectiveness of the policing initiative and any displacement or diffusion observed. For the 16 studies for which we were able to gain pre and post measures of crime for each of a minimum of three area types (a treatment, control and catchment area) we produced odds ratio effect sizes which were used in a meta‐analysis. For the meta‐analysis we reported the mean effect size for both the treatment areas and the catchment areas. This summarized the effectiveness of the policing interventions and the displacement/diffusion effect respectively. Because a number of studies had more than one primary outcome, we reported the largest effect and the smallest effect in each case. We also performed permutation tests using combinations in which one primary outcome was chosen from each study. Other tests assessed the effects of study design, intervention type, size of intervention and publication bias. A further quantitative analysis of these 16 studies summarised the mean Weighted Displacement Quotient (WDQ) a measure developed in earlier work by two of the study authors. Finally, a proportional change analysis looked at increases and decreases in crime in treatment and catchment areas for the 36 studies for which count data were available. This analysis did not require data to be available for a control area. Main Results The main findings of the meta‐analysis suggested that on average geographically focused policing initiatives for which data were available were (1) associated with significant reductions in crime and disorder and that (2) overall, changes in catchment areas were non‐significant but there was a trend in favour of a diffusion of benefit. For the weighted displacement quotient analyses, the weight of the evidence suggests that where changes are observed in catchment areas that exceed those that might be expected in the absence of intervention, a diffusion of crime control benefit rather than displacement appears to be the more likely outcome. The results of the proportional change analysis suggest that the majority of eligible studies experienced a decrease in crime in the treatment area indicating possible success of the scheme. The majority also experience a decrease in the catchment areas suggesting the possibility of a diffusion of benefit. These findings, which could not be statistically tested, are consistent with all others reported here, and with those from the narrative review. Conclusions In summary the message from this review is a positive one to those involved in the sort of operational policing initiatives considered, the main point being that displacement is far from inevitable as a result of such endeavor, and, in fact that the opposite, a diffusion of crime control benefits appears to be the more likely consequence.
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Objective: To assess the effect of a permanent gun-carrying restriction on gun-related mortality in Colombia between 2008 and 2014, and determine differences in the effect of the restriction by place of death and sex. Methods: In 2012, Bogotá and Medellín introduced a permanent gun-carrying restriction. We compared gun-related mortality rates in these cities (intervention cities) with the rates in all other Colombian cities with more than 500 000 inhabitants (control cities). We used data from the Colombian National Department of Statistics to calculate monthly gun-related mortality rates between 2008 and 2014 for intervention and control cities. We used a differences-in-differences method with fixed effects to assess differences in gun-related mortality in intervention and control cities before and after the introduction of the gun-carrying restriction. We stratified effects by place of death (public area or residence) and sex. We made robustness checks to test the assumptions of the models. Findings: Gun-related deaths in the control and intervention cities decreased between 2008 and 2014; however, the decrease was greater in the intervention cities (from 20.29 to 14.93 per 100 000 population; 26.4%) than in the control cities (from 37.88 to 34.56 per 100 000 population; 8.8%). The restriction led to a 22.3% reduction in the monthly gun-related mortality rate in Bogotá and Medellín. The reduction was greater in public areas and for males. Robustness checks supported the assumptions of the models. Conclusion: The permanent restriction on carrying guns reduced gun-related deaths. This policy could be used to reduce gun-related injuries in urban centres of other countries with large numbers of gun-related deaths.
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Introduction to the Logistic Regression Model Multiple Logistic Regression Interpretation of the Fitted Logistic Regression Model Model-Building Strategies and Methods for Logistic Regression Assessing the Fit of the Model Application of Logistic Regression with Different Sampling Models Logistic Regression for Matched Case-Control Studies Special Topics References Index.
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The regression models appropriate for counted data have seen little use in psychology. This article describes problems that occur when ordinary linear regression is used to analyze count data and presents 3 alternative regression models. The simplest, the Poisson regression model, is likely to be misleading unless restrictive assumptions are met because individual counts are usually more variable ("overdispersed") than is implied by the model. This model can be modified in 2 ways to accomodate this problem. In the overdispersed model, a factor can be estimated that corrects the regression model's inferential statistics. In the second alternative, the negative binomial regression model, a random term reflecting unexplained between-subject differences is included in the regression model. The authors compare the advantages of these approaches.
Introduction Assumptions EM and Inference by Data Augmentation Methods for Normal Data More on the Normal Model Methods for Categorical Data Loglinear Models Methods for Mixed Data Further Topics Appendices References Index
The relationship between a response variable and one or more continuous covariates is often curved. Attempts to represent curvature in single- or multiple-regression models are usually made by means of polynomials of the covariates, typically quadratics. However, low order polynomials offer a limited family of shapes, and high order polynomials may fit poorly at the extreme values of the covariates. We propose an extended family of curves, which we call fractional polynomials, whose power terms are restricted to a small predefined set of integer and non-integer values. The powers are selected so that conventional polynomials are a subset of the family. Regression models using fractional polynomials of the covariates have appeared in the literature in an ad hoc fashion over a long period; we provide a unified description and a degree of formalization for them. They are shown to have considerable flexibility and are straightforward to fit using standard methods. We suggest an iterative algorithm for covariate selection and model fitting when several covariates are available. We give six examples of the use of fractional polynomial models in three types of regression analysis: normal errors, logistic and Cox regression. The examples all relate to medical data: fetal measurements, immunoglobulin concentrations in children, diabetes in children, infertility in women, myelomatosis (a type of leukaemia) and leg ulcers.
Introduction General Conditions for the Randomization-Validity of Infinite-m Repeated-Imputation Inferences Examples of Proper and Improper Imputation Methods in a Simple Case with Ignorable Nonresponse Further Discussion of Proper Imputation Methods The Asymptotic Distribution of (Q̄m, Ūm, Bm) for Proper Imputation Methods Evaluations of Finite-m Inferences with Scalar Estimands Evaluation of Significance Levels from the Moment-Based Statistics Dm and Δm with Multicomponent Estimands Evaluation of Significance Levels Based on Repeated Significance Levels