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“An investigation of the relative strength index”
AUTH ORS Bing Anderson
Shuyun Li
ARTICLE INFO Bing Anderson and Shuyun Li (2015). An investigation of the relative strength
index. Banks and Bank Systems, 10(1), 92-96
JOURNAL "Banks and Bank Systems"
FOUNDER LLC “Consulting Publishing Company “Business Perspectives”
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© The author(s) 2019. This publication is an open access article.
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Banks and Bank Systems, Volume 10, Issue 1, 2015
92
Bing Anderson (USA), Shuyun Li (China)
An investigation of the relative strength index
Abstract
Using daily data for the Swiss franc/US dollar exchange rate, this paper studies the trading profitability of the technical
indicator Relative Strength Index (RSI). The authors find that for the past decade or so, using the standard configura-
tion of RSI < = 30 and RSI > = 70 as buy or sell threshold, RSI offers no trading profit, but a small loss instead. How-
ever, when the buy/sell threshold parameters are altered, to deviate from the combination most commonly used, using
RSI as the trading signal still yields profits. The authors also provide an explanation of this phenomenon. One implica-
tion of our findings is that consistent profit opportunities should no longer exist in what is already commonly and wide-
ly known, but taking a path less travelled could still lead to profit opportunities not yet discovered and utilized.
Keywords: currency market, financial indicator, market efficiency.
JEL Classification: G14, G15, F31.
Introduction
Technical analysis has long been a part of the
finance practice. It has been studied in the academic
finance literature, too. For example, Park and Irwin
(2007) surveyed both the early and the modern stu-
dies on technical analysis, and found that “early
studies indicate that technical trading strategies are
profitable in foreign exchange markets and futures
markets, but not in stock markets. Modern studies
indicate that technical trading strategies consistently
generate economic profits in a variety of speculative
markets at least until the early 1990s”.
The opposite of technical analysis is the fundamen-
tal analysis. However, fundamental analysis and
technical analysis are not necessarily incompatible
with each other. It is documented by de Zwart,
Markwat, Swinkels and van Dijk (2009) that com-
bining technical analysis with fundamental analysis
enhances the profitability of trading and investment
strategies.
Literature review
Falbo and Pelizzari (2011) mention that there are
many different methods of technical analysis, or dif-
ferent technical indicators. Not surprisingly, the profit-
ability of technical indicators has long been subject to
debate in the academic literature. It is likely also true
that the profitability of technical indicators actually
changes over time, as suggested by Lim and Brooks
(2011).
Mitra (2011) suggests that moving average based
technical trading rules are profitable in the stock mar-
ket of India. Analyzing a survey of 692 fund managers
in five countries, Menkhoff (2010) finds that the vast
majority of them do use technical analysis, which is
indirect evidence that technical analysis is useful in
actual trading and investment. Szakmary, Shen and
Sharma (2010) suggest that trend-following technical
trading strategies are profitable in the commodity
Bing Anderson, Shuyun Li, 2015.
futures market. And, Menkhoff and Taylor (2007) try
to explain why technical analysis could be profitable.
On the contrary, Pukthuanthong-Le and Thomas
(2008) find that “the profitability of trend following
eroded for major currencies and their associated cross
exchange rates around the mid-1990s”. Park and Irwin
(2010) also suggest “that technical trading rules gen-
erally have not been profitable in the U.S. futures
markets” Neely, Weller and Ulrich (2009) discover
that market adapts over time and the profitability of
technical trading rules changes over time.
1. Objectives of this study
This paper contributes to this important debate on the
profitability of technical analysis by focusing on one
particular technical indicator: the Relative Strength
Index (RSI). The RSI was created by Wilder and first
published by him in 1978. Despite that it is an impor-
tant technical indicator that has been around for dec-
ades, we are aware of only one study that is dedicated
to the RSI itself, a study by Rodriguez-Gonzalez,
Garcia-Crespo, Colomo-Palacios, Iglesias and
Gomez-Berbis (2011). Their study, however, is not a
study about the profitability of the RSI itself, but in-
stead is a study on modifying the RSI using neural
networks to make it forward-looking.
This paper also contributes to the important topic of
market efficiency, in the context of the currency mar-
ket. If the market is completely efficient, we should
find no profitability for the Relative Strength Index.
On the other hand, if profitability exists, that is evi-
dence that the market is not completely efficient. It
is also possible, and perhaps quite likely, that mar-
ket, being an aggregate of its participants, behaves
just like an individual participant, or a human be-
ing, in that it takes time for the market to absorb
and adapt to information, and therefore become
more efficient than before, but this process of
learning never ends. The outcome of this study
should shed light on this interesting hypothesis,
and contribute to the discussion on market efficiency.
Banks and Bank Systems, Volume 10, Issue 1, 2015
93
2. Data and research method
Calculation of the Relative Strength Index (RSI) starts
with examining the change of the closing price from
one day to the next. For each day, an up change UC
and a down change DC are calculated. For a day when
the closing price is higher than that of the previous
day, DC is zero, and UC is that day’s close minus the
previous day’s close. That is, UC is how much the
closing price has increased from the previous day to
this day.
UC = closetoday closeyesterday, (1)
DC = 0.
On the other hand, for a day when the closing price is
lower than that of the previous day, UC is zero, and
DC is the previous day’s close minus that day’s close.
That is, DC is how much the closing price has de-
creased from the previous day to this day, in its abso-
lute value.
UC = 0,
DC = closeyesterday closetoday. (2)
Both UC and DC are always non-negative. For a day
when that day’s closing price is the same as that of the
previous day, both UC and DC are zero.
A relative strength RS is defined as the ratio of the
n-day exponential moving average of the UC time
series and the n-day exponential moving average of
the DC time series. Very often, a 14-day exponential
moving average is used.
RS = EMA (UC, n) / EMA (DC, n). (3)
Finally, RS is converted to the RSI by:
RSI = 100 100/ (1 + RS). (4)
We obtain the daily data on US Dollar/Swiss Franc
exchange rate, from January 5, 1998 to May 22, 2009,
courtesy of the TradeStation Group. We will be using
mostly observation numbers rather than date to refer to
data points, with Observation 1 being that for January
5, 1998, and Observation 2955 being that for May 22,
2009.
Figure 1 plots the exchange rate itself over time in
units of pips. For example, a reading of 15000 on the
vertical axis means the actual exchange rate is 1.5000.
That is, it takes 1.5 Swiss Francs (CHF) to buy one US
Dollar (USD). As can be seen from the figure, for the
first 800 to 900 observations, the general trend is that
CHF is depreciating against the USD. For the rest
of the time, CHF is in general appreciating
against the USD.
Fig. 1. The daily US Dollar/Swiss Franc exchange rate in units of pips
Figure 2 plots the Relative Strength Index (RSI)
computed from the daily exchange rate. RSI was
computed based on the past 14 time periods, which
is a time period length commonly used in practice.
The figure shows that RSI, during this decade for
USD/CHF exchange rate, can go occasionally as
high as 90 or above, or 10 or below, which is consi-
dered rather extreme. If we consider the times when
RSI goes above 80 or below 20, there are more of
these cases, but still not very common. Just from a
visual inspection of the figure, in the majority of the
observations, RSI is indeed between 30 and 70,
which is consistent with the conventional wisdom
that an RSI below 30 or above 70 represents over-
sold or overbought conditions and therefore are
buying or selling opportunities.
Banks and Bank Systems, Volume 10, Issue 1, 2015
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Fig. 2. The Relative Strength Index (RSI) technical indicator for the daily US Dollar/Swiss Franc exchange rate.
However, if one buys when RSI reaches 30 and sells
when RSI reaches 70, as conventional wisdom dic-
tates, will that be a profitable trading strategy? We
investigate.
We start with Observation 15, the first observation
where RSI is available and computed, and progress
over time observation by observation. The first time
we encounter an RSI value that is 30 or below, or 70
or above, a buy or sell transaction is carried out. For
example, without loss of generality, the first such RSI
we encounter is 70 or above, and we sell at the price
corresponding to that RSI, creating a short position.
Once such an open position is created, it can only be
closed when an opposite trading signal is encountered.
Continuing with our example, once we have a short
position, the position will remain open until we en-
counter an RSI that is 30 or below, when we close the
short position at the corresponding exchange rate,
book the profit or loss, then also open a long position
at that same exchange rate. The long position won’t be
closed until an RSI that is 70 or above is encountered,
when we close the long position at the exchange rate
at that time, book the profit or loss, then also open a
short position at that same exchange rate. And the
process goes on and on. The last open position, be-
cause it cannot be closed based on the data we have,
will not count either as a profit or a loss. The way
profit or loss is booked is simply take the difference in
pips of the entry and exit points. For example, if we
long at 1.5000 and close the position at 1.5145, that is
a profit of 145 pips. If we long at 1.5000 and close the
position at 1.4000, that is a loss of 1000 pips.
Results
The trading simulation with RSI at 30 and 70 being
the buy/sell threshold comes back disappointing. The
total profit is -3009 pips, or in other words a loss of
3009 pips. If we count opening a position and then
later closing that same position as a trade, there are 53
trades in total. The trade with the biggest loss has a
loss of 1702 pips.
The RSI as a technical indicator was first published by
Wilder in 1978. For more than three decades, the in-
vestment community has been using it, most common-
ly with 30 and 70 being the buy/sell threshold. It is not
surprising that an indicator that has been known for so
long and has been used so widely can no longer give
one any edge in trading.
But would it be possible for a different threshold com-
bination to still be generating trading profits? We ex-
periment with 20/80 first.
The trading simulation with RSI at 20 and 80 being
the buy/sell threshold comes back with a small profit.
The total profit is 2387 pips. If we count opening a
position and then later closing that same position as a
trade, there are 23 trades in total. The trade with the
biggest loss has a loss of a staggering 2442 pips,
which is even bigger than the total profit. This para-
meter combination is eventually a bit profitable, how-
ever. One has to be able to stomach quite a bit of loss
in order to reach that eventual profit. The reduced
number of trades is because the threshold for trading is
now higher than the previous case of 30/70, and there-
fore less trades meet the standard and are carried out.
We move one step further in the same direction, and
try the 10/90 combination next. The trading simulation
with RSI at 10 and 90 being the buy/sell threshold
comes back with an even smaller profit. The total
profit is 1094 pips. There are only 6 trades in total.
The trade with the biggest loss has a loss of 3622 pips,
which is even bigger than that of the 20/80 parameter
combination.
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Given the degeneration of performance when we
move from the 20/80 parameter combination to the
10/90 parameter combination, we naturally decide to
go the other way and try 40/60 instead.
Surprisingly, the trading simulation with RSI at 40 and
60 being the buy/sell threshold performs the best
among all the parameter combinations we have tested
so far. The total profit is 5206 pips. There are 125
trades in total. The trade with the biggest loss has a
loss of 1876 pips.
To be complete, and to give us an idea about the pa-
rameter stability in terms of profitability, we investi-
gate the cases in between, too. The first of these cases
is the 35/65 parameter combination. The total profit
is 6621 pips. There are 93 trades in total. The trade
with the biggest loss has a loss of 1461 pips. The
second of these intermediate cases is the 25/75
parameter combination. For this case, the total
profit is 863 pips. There are 41 trades in total. The
trade with the biggest loss has a loss of 1380 pips.
It is interesting that the famous and widely used
30/70 parameter combination generates a loss, but
a little bit above and a little below that, they are
both profitable cases. We suspect this is exactly
because that the 30/70 parameter combination is so
famous and so widely used. When a market ineffi-
ciency is known and exploited by many for a long
period of time, the very activities of making profit
off this market inefficiency tend to reduce the
market inefficiency itself, and eventually remove
the profit opportunity. It has to be this way. Oth-
erwise, if a market inefficiency can be used by
many people to make as much money as they
please, and the market inefficiency and the profit
opportunity never reduces or disappears, it would
have become an infinite fountain of free wealth,
which exists only in myth, not in reality.
To complete our investigation, we carry out trading
simulation with RSI at 15 and 85 being the buy/sell
threshold. It is also a profitable case. The total profit is
4616 pips. There are 10 trades in total. The trade with
the biggest loss has a loss of 1946 pips.
Conclusion and recommendation
The significance of the findings in this paper is two-
folded. On one hand, we find that for the past decade
or so, using the standard configuration of RSI < = 30
and RSI > = 70 as buy or sell threshold, RSI offers no
trading profit, but a small loss instead. Once a technic-
al indicator is well known and a standard parameter
configuration for the technical indicator is well used in
practice, its profitability diminishes.
However, there is hope left. As the rest of our findings
indicate, when the buy/sell threshold parameters are
altered, to deviate from the combination most com-
monly used, using RSI as the trading signal still yields
profits.
This is merely an initial investigation of the Relative
Strength Index. Much more can be possibly done in
subsequent studies. For example, the same trading
simulation can be carried out on price data in the stock
or the futures markets. It is also possible for more
complicated trading rules to be derived based on RSI,
but not completely dependent on the RSI. For exam-
ple, we could use RSI as a threshold to open a posi-
tion, but once a position is opened, a trailing stop loss
order, rather than another RSI threshold, will be used
for determining when to close the position.
For practitioners, the recommendation coming out of
this study is to take the path less travelled. What is
already commonly known and commonly used hardly
offers any opportunity for profit any more. However,
even for an indicator as widely known as the RSI,
altering parameter configuration to an uncommon
combination still finds profits that have yet to be dis-
covered and picked up.
For academics, this study has implications on the
theory of market efficiency. What can be seen from
this study is that the market is neither completely effi-
cient, nor persistently inefficient, but rather an entity
that learns and adapts, and gradually becomes more
efficient but never absolutely and perfectly efficient.
Each and every participant in the market learns and
adapts in this way. The market is just an aggregate of
its participants. Why should not the market behave in
this way too?
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