John N. Ng'ombe

John N. Ng'ombe
North Carolina Agricultural and Technical State University | NC A&T · Department of Agribusiness, Applied Economics and Agriscience Education

Doctor of Philosophy
Agricultural economics, applied econometrics, Bayesian analysis, machine learning, and production econometrics.

About

52
Publications
26,481
Reads
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319
Citations
Introduction
John uses econometrics, statistics, and economic theory to answer interdisciplinary research questions. His recent publications are: Impact of improved rice varieties on household food security in Northern Ghana: A doubly robust analysis, Crop Diversification Improves Technical Efficiency and Reduces Income Variability in Northern Ghana, and The Effect of Including Irrelevant Alternatives in Discrete Choice Models of Recreation Demand.
Additional affiliations
June 2019 - August 2019
Oklahoma State University - Stillwater
Position
  • Researcher
August 2015 - March 2016
Oklahoma State University - Stillwater
Position
  • Research Assistant and Ph.D Student
January 2014 - August 2015
University of Zambia
Position
  • Lecturer
Education
August 2020 - August 2020
Oklahoma State University - Stillwater
Field of study
  • Agricultural Economics

Publications

Publications (52)
Article
Full-text available
Objective The purpose of this study is to examine how cannabis legalization and corresponding taxation would affect the supply-side of the cannabis market. Specifically, the study considers various scenarios in which Oklahoma legalizes recreational cannabis for adult use and simulates changes in state-level market sales for other legal states and t...
Article
The soil water retention curve (SWRC) is a core concept of unsaturated soil mechanics. To date, while various SWRC prediction models have been developed, they require large datasets to generate accurate results. Most importantly, and uncoincidentally, obtaining large SWRC datasets from experimental procedures might prove costly, time-consuming, and...
Article
Full-text available
This study examines disaggregated impacts of participation in off-farm employment on household vulnerability to food poverty in Ghana. We use household-level data collected from smallholder farmers in Ghana. This study employs the multinomial endogenous switching regression model to account for selection bias due to both observed and unob-served he...
Article
Full-text available
Faced with food supply disruptions due in part to geopolitics and political instability in its traditional food source markets in the Kingdom of Saudi Arabia and the United Arab Emirates, Qatar-a wealthy, highly import-dependent open economy-plans to identify a set of alternative markets that can assure it of a stable food supply chain and food sec...
Article
Full-text available
For many decades, researchers have relied on small-scale agronomic experiments to provide input management recommendations to farmers. However, such experiments have most often provided production functions with large standard errors in addition to uncertainty about how well the estimates apply to different fields. To avoid such limitations, there...
Article
Full-text available
We measure bias and efficiency of parameter estimates in the conditional logit (CL) and independent availability logit (IAL) models. Our Monte Carlo experiments consider both no choice set formation where individuals choose from the full set of alternatives, and when choice sets are stochastically formed and individuals choose from a subset of all...
Article
Full-text available
Smallholder farmers' preferences for participation in contract farming may take the form of proportional data-whereby farmers only sell some proportions or fractions of output to contractors. We analyze determinants for preferences for zero (potential corner solution) and proportional amounts of milk that farmers sell through contract farming using...
Article
Full-text available
Smallholder farmers’ preferences for participation in contract farming may take the form of proportional data – whereby farmers only sell some proportions or fractions of output to contractors. We analyze determinants for preferences for zero (potential corner solution) and proportional amounts of milk that farmers sell through contract farming usi...
Article
Full-text available
We examined gender-based household welfare differences in Ghana among smallholder households. We measured disparities in welfare outcomes (food poverty, vulnerability, and food consumption inequality) across male and female household heads and identified the set of covariates influencing them. The study utilizes a dataset from a farm household surv...
Article
Full-text available
Bayesian analysis provides a principled way to quantify uncertainty and incorporate data and prior knowledge into parameter estimates. This paper makes the latest in Bayesian methods easier for others to use with a focus on a stochastic plateau crop production function. Previous studies have used Bayesian techniques to model stochastic plateau func...
Article
Purpose-The authors examine the factors influencing membership in farmer organizations (FO) and their effects on the decision to adopt farm technologies by rice farmers in Ghana. Design/methodology/approach-This study uses a farm survey of 900 households from Northern Ghana and a recursive bivariate probit (RBP) model that accounts for selection...
Article
Full-text available
The traditional approach to modeling productive efficiency assumes that technology is constant across the sample. However, farms in different regions may face different production opportunities , and the technologies they employ may differ due to environmental factors. Therefore, rather than using a traditional stochastic frontier model in such cas...
Article
Agricultural intensification has been encouraged through the promotion of various agricultural technologies, but the synergies between different technologies have not been fully explored among various specific crops. Using the multinomial endogenous switching regression model complemented with the multivalued inverse probability regression model, t...
Article
Full-text available
It is well established that the global practice of burning crop residues, such as orchard biomass, harms human health and the environment. A bioeconomy for orchard biomass may reduce open burning, facilitate the recovery of nutrients that improve soil health, and boost economic growth. We present a techno-economic analysis for converting orchard wa...
Poster
Full-text available
Contract farming (CF) is a pre-output agreement between agricultural producers and buyers. CF helps to integrate farmers in developing countries to global agricultural value chains (Barrett et al. 2012). But research also shows that value chain intermediary agents acquire superior earnings than farmers. This study employs a Bayesian zero-one-inflat...
Poster
Agricultural and Applied Economics Association (AAEA) Conferences > 2021 Annual Meeting, August 1-3, Austin, Texas
Article
Full-text available
Crop diversification has been shown to help mitigate climate change effects for farmers. While previous research shows that crop diversification may increase or decrease technical efficiency in different regions, research on whether crop diversification involves a tradeoff between technical efficiency and income variability is limited. Using agricu...
Article
Full-text available
The ingredients extracted from genus Echinacea are classified as drugs in Korea but as functional health foods in many countries including USA and European countries. In Korea, the classification of the ingredients of this plant has recently become an important issue due to a surge in consumer demand for the formulations made of the ingredients dur...
Article
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This study uses structural equation modelling (SEM) and path diagram techniques to examine challenges faced by women in the agricultural sector cooperatives in Southeast Nigeria. The data are from a cross-section survey of randomly selected women cooperative members. Results suggest that women with poor economic status are less likely to have acces...
Article
Full-text available
This paper examines the effects of regional characteristics on the spread of the highly pathogenic avian influenza (HPAI) during Korea’s 2016–2017 outbreak. A spatial econometric model is used to determine the effects of regional characteristics on HPAI dispersion using data from 162 counties in Korea. Results indicate the existence of spatial depe...
Article
Full-text available
This study analyzes the consumer characteristics of health functional food intake by major product, and measures the national health expenditure saved due to the intake. Our survey of 1,210 consumers covers the current state of their health functional food intake and their consequently reduced medical expenses. Using a probit model, this study anal...
Article
Full-text available
This study determines the impact of the adoption of improved rice varieties on household food security using farm‐level data from 900 households in Northern Ghana. We employed the doubly robust inverse probability weighted regression adjustment procedure complementary with a propensity score matching approach on two indicators of food security (hou...
Article
Full-text available
An issue with ordinary least squares estimations in hedonic pricing model literature is that they do not account for sample selection bias. In broodmare auctions, the purchase decision and whether a price is realized or zero is endogenous. This paper contributes to the hedonic broodmare price analysis literature by implementing the Heckman sample s...
Article
While contract farming and interlocked contractual arrangements (ICAs) are generally perceived to resolve persistent market failures and improve smallholder farmers' welfare in developing countries, uncertainties remain as to whether these arrangements enhance welfare because of farmers' low marketed volumes and margins. To account for potential se...
Article
Full-text available
This study analyzes the self-reported intake of dietary supplements (DS) and their effects on perceived health well-being from a survey with 1210 adult respondents in Korea. To account for selectivity bias from observable confounders, we use a propensity score matching (PSM) model. Our findings show that demographics, health concerns, family histor...
Article
Full-text available
Crop diversification is a climate-smart agricultural technique which helps to improve resilience for farmers in the face of volatile weather due to climate change. Previous research on its effects on technical efficiency has shown mixed results. Despite burgeoning literature on the subject, an important research question that remains uninvestigated...
Article
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China is one of the largest sources of outbound tourists coming to the United States. We used data from a choice experiment to determine whether Chinese tourists are interested and willing to pay for agritourism tour packages in which the U.S. state of Oklahoma is the rural destination. Our research is important because agritourism is a growing sou...
Preprint
Full-text available
Maize (Zea mays L.) is one of the commonly grown grain crops and remains a source of staple food and food security for most countries in sub-Saharan Africa (SSA). But climate change threatens agricultural potential in SSA thereby risking food security especially that most maize production is rain-fed in these countries. Thus, numerous studies have...
Article
Full-text available
The tobacco epidemic is one of the most prominent public health threats the world has ever faced. Public health policy that seeks to limit the problem may have to target not only the price of tobacco but also the initiation stage in a smoker’s life—the adolescent stage. Most research on teen smoking focuses on initiation and other stories. Moreover...
Conference Paper
Full-text available
This paper seeks to make the latest in Bayesian methods easier for others to use with a focus on a stochastic plateau production function. A few studies have used Bayesian techniques to model a stochastic plateau function. No published work provides estimation of a stochastic plateau function by taking advantage of computationally efficient Hamilto...
Article
Full-text available
While climate change threatens global food security, health, and nutrition outcomes, Africa is more vulnerable because its economies largely depend on rain-fed agriculture. Thus, there is need for agricultural producers in Africa to employ robust adaptive measures that withstand the risks of climate change. However, the success of adaptation measur...
Preprint
The tobacco epidemic is one of the leading public health threats the world has ever faced and public health policy that seeks to limit the problem may not only have to target the price of tobacco but also the initiation stage in a smoker’s life – the adolescent stage. This research contributes to the health economics literature by using a Bayesian...
Preprint
Corn yields in developing countries are lower than in developed countries partly due to planting methods that involve hand dropping of multiple seeds per hill. Researchers from Oklahoma State University (OSU) recently developed the Greenseeder Hand Planter (GHP) to replace such methods. The first essay determines economic breakeven levels of seed a...
Chapter
Full-text available
Maize (Zea mays L.) is one of the commonly grown grain crops and remains a source of staple food and food security for most countries in sub-Saharan Africa (SSA). But climate change threatens agricultural potential in SSA thereby risking food security especially that most maize production is rain-fed in these countries. Thus, numerous studies have...
Poster
Full-text available
We determine a Bayesian optimal dynamic sampling procedure for on-farm field experimentation.
Article
Full-text available
The marked increase in earthquakes in Oklahoma since 2009 is widely associated with underground wastewater injection by oil and gas companies. Using the mixed logit model, we determine willingness to accept potential job and tax revenue losses in return for fewer earthquakes and reduced risk of damaging earthquakes in Oklahoma. Results suggest peop...
Article
Scientific evidence suggests earthquakes occurring in Oklahoma since 2009 are not “acts of God”, but very likely triggered by wastewater injection in disposal wells by oil and gas (O&G) companies. While sustaining the O&G industry's contribution to the economy is generally important, achieving environmental and public protection may in part rely on...
Article
Full-text available
Corn (Zea mays L.) yields in developing countries are lower than in developed countries, in part due to planting methods that involve hand dropping of multiple seeds per hill. The Greenseeder hand planter (GHP) was developed to reduce seeding rates and long-term health risks from using bare hands to drop pesticide-treated seeds. When used to apply...
Article
Full-text available
Smallholder irrigation schemes potentially improve the livelihoods of rural communities in developing countries. However, they face challenges such as infrastructural decline, lack of funding, lack of markets, shortage of water, underutilization of land, and inefficient irrigation systems. In Zimbabwe, the government carried out rehabilitation prog...
Conference Paper
Full-text available
Before 2009, Oklahoma recorded single digit numbers of earthquakes. The number of earthquakes reached triple digits by 2015 and the U.S. Geological Survey (USGS) points to underground injection of wastewater from oil and natural gas drilling companies in Oklahoma as the main cause. Although reducing wastewater injections could significantly reduce...
Presentation
Full-text available
This presentation was about willingness to accept job losses and tax revenue for regulated wastewater injection into the underground by Oklahoma residents. The presentation was made at Midwest Economics Annual Meeting in Evanston, IL.
Article
We determine and compare technical efficiency (TE), technology gap ratios (TGRs) and meta-frontier technical efficiency (MTEs) of maize production between regions using nationally representative panel data collected from 4001 smallholder farm households in Zambia. We estimate the stochastic meta-frontier and region-specific stochastic frontiers bas...
Article
Full-text available
Most empirical work on sources of economic growth for different countries lack country-specific empirical evidence to guide policy choices in individual developing countries and previous studies of factor productivity tend to focus on the entire economy or a single sector. This provides fewer insights about a country’s structural evolution. Unlike...
Article
Full-text available
We determine the impacts of conservation farming (CF) practices on crop net revenue of smallholder farm households using nationally representative household and plot survey data in Zambia. We estimate a multinomial endogenous switching regression model of farm household's choice of combinations of CF practices and their impacts on crop net revenue....
Preprint
Full-text available
Most empirical work on sources of economic growth for different countries lack country-specific empirical evidence to guide policy choices in individual developing countries and previous studies of factor productivity tend to focus on the entire economy or a single sector. In this study, we use the recently developed growth accounting tools to expl...
Article
Full-text available
Minimum tillage and other conservation agriculture practices are not only associated with income gains but are also claimed to be the panacea to the declining agricultural productivity and soil degradation problems in Africa and across the world. The few studies on technical efficiency related to the agricultural sector performance in Zambia have n...
Article
Full-text available
Despite the efforts to promote adoption of conservation farming (CF) by public and private organizations, the adoption rate among Zambian smallholder farm households has been low. This study used nationally representative data to identify the factors that affect adoption of CF by smallholder farm households in Zambia. Propensity Score Matching (PSM...

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Projects

Projects (5)
Project
To explore smallholder households vulnerability to poverty in Northern Ghana
Project
To develop a Bayesian dynamic experimental design that will enable farmers appreciate the value of information of their field trials.
Project
To deliver viable hand planter to replace indigenous planting and fertilization methods and improve grain yields and fertilizer N use efficiency.