Heckman Sample Selection Research Articles

Using instruments for selection to adjust for selection bias in Mendelian randomization.

Selection bias is a common concern in epidemiologic studies. In the literature, selection bias is often viewed as a missing data problem. Popular approaches to adjust for bias due to missing data, such as inverse probability weighting, rely on the assumption that data are missing at random and can yield biased results if this assumption is violated. In observational studies with outcome data missing not at random, Heckman's sample selection model can be used to adjust for bias due to missing data. In this paper, we review Heckman's method and a similar approach proposed by Tchetgen Tchetgen and Wirth (2017). We then discuss how to apply these methods to Mendelian randomization analyses using individual-level data, with missing data for either the exposure or outcome or both. We explore whether genetic variants associated with participation can be used as instruments for selection. We then describe how to obtain missingness-adjusted Wald ratio, two-stage least squares and inverse variance weighted estimates. The two methods are evaluated and compared in simulations, with results suggesting that they can both mitigate selection bias but may yield parameter estimates with large standard errors in some settings. In an illustrative real-data application, we investigate the effects of body mass index on smoking using data from the Avon Longitudinal Study of Parents and Children.

The effects of social capital and family income on farmers’ participation in rural public goods provision

Farmers' participation in rural public goods provision (PGP) is vital to improving rural public goods conditions and achieving rural revitalization in China. The factors influencing farmers' participation are, however, far from clear. This paper aims to investigate how social capital and income, the two most prominent factors, affect rural residents' participation in PGP. We use the Heckman sample selection model to empirically estimate the effects of both social capital and family income on farmers' participation and contribution to PGP based on a household survey conducted in four representative provinces in China. We further investigate the moderating effect of village location and elite ability on the effect of social capital on farmers' participation. Our results show that social capital generally has a positive impact on farmers' participation. Specifically, improving the formal norm, size of networks, and density of network would increase farmers' participation propensity. Enriching norms, particularly formal norms, can significantly improve farmers' contribution to public goods. Surprisingly, family income, mainly non-farm income, has a slightly negative effect on farmers' participation. Moreover, village-county distance can undermine the effect of social norms on farmers' participation, while elite ability can enhance the effect of social trust on farmers' participation. Thus, we suggest authorities should focus on enhancing social capital in the rural community to promote farmers’ participation in PGP.

Consumers´ willingness to pay for snacks enriched with insects: A trending and sustainable protein source

High-protein snacks appeal to consumers seeking to increase the protein intake in their diet. The high environmental impact of conventional protein sources is urging the need to explore more sustainable alternatives such as edible insects. In this study, the willingness to pay for yogurt enriched with insect protein was estimated. It also determined the effect of socio-demographics and extrinsic product attributes on the purchase decision and expenditure using the Heckman sample selection model. Data was collected through an online survey from 1,909 consumers in Catalonia, Spain using Qualtrics´ consumer panel. The results showed that 55.7% of the participants were willing to purchase the product and that the average premium price computed was 0.36€ or 24% extra compared to the conventional price of yogurt. Findings also revealed that the probability of purchasing yogurt enriched with insect protein increases with younger adults, male consumers, residing in rural areas, having a child member in the family unit, and an active employment situation. Moreover, expenditure increases when the importance of the local and ecological attributes of food is higher, while lower for the price attribute. The results of this study offer food producers valuable insights into consumers’ willingness to pay for novel protein snacks.

The Effect of Family Members’ Perceived Upward Mobility on Marriage and Childbirth Using Heckman Sample Selection Model

The Effect of Family Members’ Perceived Upward Mobility on Marriage and Childbirth Using Heckman Sample Selection Model

Corporate governance and corporate social responsibility: Evidence from directors' and officers' liability insurance

AbstractTheoretical theories underpin the governance effect of directors' and officers' (D&O) liability insurance include agency costs and stakeholder interests. Motivated by mixed evidence on the corporate governance effects of D&O, we ask whether and how the directors' and officers' (D&O) liability insurance affects corporate social responsibility (CSR) performance in China, one of the largest and fastest growing economies in the world. We develop two contrasting hypotheses: (1) supervision and incentives versus (2) opportunism. To test these hypotheses, we rely on Chinese A‐share market data and fixed effect panel regressions, along with a battery of robustness checks, including Heckman sample selection bias, two‐stage least square instrumental variable (2SLS‐IV), difference‐in‐difference (DiD), propensity score matching (PSM) analyses. Consistent with supervision and incentives hypotheses and stakeholder theory, we find that D&O liability insurance significantly increases firm's CSR performance and firms renewing D&O liability insurance with the same insurers tend to have better CSR performance. Two possible mechanisms supporting this positive relation between D&O liability insurance and CSR performance are information transparency and accounting conservatism. Aside from theoretical contributions, our findings offer important practical contributions such as promoting D&O as external governance and ensuring the functions of D&O insurance comprehensively and correctly understood. Integrating D&O insurance with CSR can be viewed as an important business strategy by mitigating risks, enhancing reputation, ensuring legal compliance, and supporting responsible decision‐making.

Global energy transition and foreign environmental regulations: Impacts on Russian regions’ export volumes

This paper analyses the impacts of trading partners’ environmental regulation on the export volumes of the Russian regions, using panel data covering about 140,000 observations in 84 Russian regions and 204 countries for the period 2013–2020. We employ the Gravity Model of international trade and Heckman Sample Selection methodology, with the fixed effects and random effects Poisson Pseudo-Maximum Likelihood techniques to analyse two subsamples of the Russian regions with different shares of environmentally sensitive goods in regional exports. As a robustness check, we utilize the non-parametric Driscoll–Kraay approach. The results of the econometric estimation demonstrate that environmental regulations enhance the export of regions with a high share of environmentally sensitive goods in export structure, while for the rest of the regions the environmental regulations negatively affect export volumes. The promoting effect is associated with a higher level of innovativeness of the regions and the role of the global energy transition process. We conclude that the environmental agenda is a challenge for some Russian regional exporters due to the lack of own environmental regulation, and to the specific features of the commodity and geographic structure of exports. To transform the negative impact into the positive one for all Russian regions, policy measures are necessary on the federal, regional, and company levels, encompassing environmental regulations and green development strategies, along with innovation and cluster policies, and the development of human capital and infrastructure.

Members’ willingness to pay for sustainability agricultural organization: A Heckman model approach

The purpose of this research analyzed the factors influencing the members’ willingness to pay capital in the agricultural cooperatives and unions. The research was performed on a sample 155 members of agricultural organizations in Igdir province of Türkiye using the Simple Random Sampling method. Members’ willingness to pay capital to their organizations were examined using the Contingent Valuation Method and effected factors were analyzed by Heckman Sample Selection model. The research showed that 56.6% of members were willing to pay capital an average of $131 for sustainability of organizations. According to the model results showed that members’ gender, agricultural income, know definition of organization, increase in income of members, pay entry capital, frequency of visiting, meeting the general assembly, cohesion of members positively affected, however, age, household, animal units, negative experience in the past with their organizations negatively affected the members’ willingness to pay capital. In order to sustainable of agricultural organizations, cohesion of members and participation to general assembly must increase. And, encouraging more young and female farmers to become a member, taking an active role cooperatives and unions in marketing and supply input could increase the members’ willingness to pay capital. In addition, training programs should be organized by agricultural organizations and government about increasing capital and economic participation.
 Keywords: Agricultural organizations; Contingent analysis; Cooperative; Heckman sample selection model; Willingness to pay capital

Corporate social responsibility, board characteristics, and family business in Thailand

AbstractExploring the relationship between corporate social responsibility (CSR) strategy, family business, and board characteristics in Thailand provides invaluable insights into how boards of family businesses integrate CSR considerations, leading to responsible business practices and sustainable development in Thailand. Relying on the top 100 listed firms in the Stock Exchange of Thailand and the Refinitiv's CSR strategy score, we find that family business firms or firms with CEO serving as the chairman of board engage less CSR strategy, being consistent with the agency cost hypothesis and the expropriation view of family businesses. Additionally, in line with the resource dependency theory, female directors, independent directors, board tenure, and board size positively influence a firm's CSR. Additional analyses including the Heckman's sample selection bias and 2SLS instrumental variable approaches show that our results are robust and are not driven by unobserved heterogeneity. More importantly, gender diversity is an exemplary governance mechanism as it is the only board characteristic with a positive effect on CSR in both family and non‐family sub‐samples. While board tenure is positively associated with CSR in the non‐family business sample, larger board size and more board independence in the family business positively influence a firm's CSR. Findings from the family business sample support the functional view of board and socioemotional wealth of family firms.

Public Agricultural Extension, Pest and Disease Experience, and Adoption of Improved Wheat Varieties

Improved varieties are considered critical for increasing crop yields worldwide. This study explored the effects of public agricultural extension and pest and disease experience on adoption of improved varieties using survey data on 525 wheat farmers in Anhui Province, China, to which the Heckman sample selection model was applied. The results showed that public agricultural extension had a significant positive relationship with adoption of improved varieties. Demonstration and training, as different forms of agricultural extension, both increased the probability of farmers adopting improved varieties, but only demonstration had a marked effect on degree of adoption. Pest and disease experience increased the probability of adoption of improved varieties by farmers and significantly enhanced the effect of public agricultural extension, but did not affect degree of adoption. Further analysis using an endogenous switching regression model revealed that adoption of improved varieties raised wheat yields by around 337.83 kg/ha. Public agricultural extension should thus be strengthened, especially for farmers with pest and disease experience, and a diversified, well-functioning agricultural extension system should be provided.

The impact of prescription drug insurance on cost related non-adherence to medications in Canada: A Heckman sample selection approach.

Unlike some other high-income counties, Canada does not provide universal prescription drug coverage. The various extent of coverage may left some Canadians vulnerable to cost-related non-adherence (CRNA) to medications. Using data from the 2015 national cycle of the Canadian Community Health Survey, we examine the impact of having private and public drug coverage on mitigating the risk of CRNA with a logit model and a Heckman selection model. CRNA was only observed in respondents who had prescriptions to fill, and respondents did not randomly make decisions on whether to get a prescription. This results in a classic sample selection problem. We found a higher estimated probability of reporting CRNA for uninsured respondents from the Heckman selection model than from the logit model. Respondents with government coverage only had a slightly higher probability of reporting CRNA relative to respondents with private coverage. These findings suggest that, without accounting for sample selection, the risk of not having drug insurance coverage is likely to be underestimated. Moreover, despite covering a less healthy cohort of respondents, the government insurance plans reduce risk of CRNA to a comparable level with private insurance.

표본 선택 모형을 통한 밀레니얼 세대의 인턴십 경험이 취업 및 임금에 미치는 영향 분석

The aim of this study is to analyze the influence of internship experiences on the employment and wages of millennials during their college years to understand the actual labor market outcomes of internships. For this purpose, we utilized data from the 2020 Graduate Occupational Mobility Survey (GOMS 2019) to estimate a probit model and a wage equation using Heckman two-stage model. First, the model validity analysis confirms that the Heckman's sample selection model is statistically significant for this study, exhibiting a negative correlation, with smaller wages having a higher probability of being selected into the sample. Second, the first-stage of Heckman’s probit model analyzed the effects of internship experiences on employment, revealing that internships positively impact employment prospects. This impact was statistically significant with regard to gender, academic grade, metropolitan region, and the father's level of education. Third, in Heckman's two-stage wage equation estimation, it was found that internship experience did not influence wages, wherein the study showed that regular employees earned approximately 22% more than non-regular employees.

The determinants of household electricity demand in Turkey: An implementation of the Heckman Sample Selection model

Residential areas have a significant share in electrical energy consumption in Turkey. At this point, determining electricity consumption demand in residential areas will significantly contribute to ensuring energy efficiency throughout the country. Accurate econometric modelling of the relationships between the various socio-economic characteristics of households and their energy consumption/expenditure can serve as a basis for policymakers when planning investments aimed at efficiency on primary energy consumption in residences. Considering these issues, this study aims to examine the electricity consumption demand in residential areas in Turkey in terms of various socio-economic and building and property characteristics variables. At this point, the fact that some households have zero electricity consumption has led to the need to use censored regression models. The Heckman Sample Selection model was used, which makes it possible to estimate the consumption decision of individuals in two stages and eliminates the parameter bias problem caused by linear regression analysis. Heckman Sample Selection modelling was carried out in the study using Turkish Statistical Institute (TURKSTAT) 2019 Household Budget Survey data. According to the results, it has been determined that annual disposable income, various demographic variables (age, education level, marital status), characteristics of the house (size) and the presence of various electrical household appliances (air conditioner, tumble dryer, deep freezer) have significant effects on electricity consumption. The systematic preparation of informative brochures on the effective use of household electrical appliances can significantly contribute to efficiency. In addition, in countries like Turkey that depend on foreign energy, providing incentives towards renewable energy sources is considered necessary to contribute to the country's economy positively.

Modelling the maize marketed surplus behaviour under risk and time preference conditions: The case of Zvimba and Mokonde districts of Zimbabwe

The Heckman sample selection technique was applied in modelling the households’ maize marketed surplus decision under risk and time preference assumption. We assumed that maize returns depend on farmers’ market selection choices. We then applied the sample selection model to explain why maize surplus households shunned the uncertain, high-return state-owned Grain Marketing Board (GMB), with delayed payment system in favour of the more certain, low-return private buyer market, with immediate payment system. In the process, we tested whether the marketed surplus decisions followed a sequential or simultaneous decision process. Using survey data collected from 433 households from Zvimba and Makonde districts, the results confirmed that households followed a sequential decision process when selling through the private buyer market and a simultaneous decision process when selling through the GMB market. These findings implied two things; firstly maize surplus households could exercise some bargaining power in the private buyer market even if they got less. Secondly, in the presence of uncertainty and payment delays, high-return incentive offered through government parastatals may not be sufficient to attract maize surplus, as households may not sufficiently respond, due to risk aversion attitude and time impatient behaviour.

Sustainable Use of Soil and Water Conservation Technologies and Its Determinants: The Case of the Handosha Watershed, Omo-Gibe River Basin, Ethiopia

For the past forty years, Ethiopia has been promoting sustainable land management activities to enhance agricultural productivity. This study was intended to identify the factors determining farmers’ adoption and continued use of soil bund measures in the Handosha watershed, Omo-Gibe river basin. A multistage sampling technique was used to select 340 households using the Heckman sample selection model. A total of 235 (69.12%) households adopted soil bunds, but only 89 (37.87%) of them were sustainably practicing soil bunds on their farm plots. Most adopters widely practiced soil bunds (49.42%), followed by stone bund (15.9%), and Fanyajuu (10%). The empirical results of the Heckman sample selection model showed that the farming experience, land tenure security, and perception of profitability of conservation measures were significantly positively affected the adoption of soil bund. Whereas, farm plot size and participation in off farm activities significantly negatively influenced the adoption of soil bund. Sustainable use of soil bund measures were significantly positively influenced by land tenure security, family size, and frequency of extension contact, whereas the distance between farm plots and home, and farm plot size were negatively affected. As a result, a design of agro-ecological-based soil and water conservation (SWC) measures was essential in reducing farmland vulnerability to soil erosion and food insecurity. It has been concluded that conservation practices should not only focus on the implementation and biophysical factors but also consider the socioeconomic interests of the farmers to improve the sustainable use of conservation technologies.

The effects of environmental information disclosure on stock price synchronicity in China

Environmental information disclosure has attracted the attention of the capital market because it can convey corporate characteristic information. But there needs to be direct evidence that environmental information disclosure can improve the market's overall efficiency. This study examines whether corporate environmental information disclosure can improve the information efficiency of the capital market. This study takes Chinese listed companies from 2008 to 2021 as samples, constructs a panel fixed effect model, and adopts multiple linear, instrumental variable method and Heckman sample selection model. We find that the disclosure of environmental information in the Chinese market reduces the information efficiency of the capital market represented by the synchronicity of stock prices. The reason is that the information after greenwashing by enterprises needs to be of better quality and more obscure, which disrupts market information. Environmental information disclosure by enterprises prone to greenwashing significantly affects stock price synchronicity, such as low institutional ownership, non-state-owned, growth, and manufacturing firms. Finally, this paper discusses the impact mechanism and confirms that stock liquidity and analyst coverage are the two paths through which environmental information disclosure impacts stock price synchronicity. This study is significant in encouraging the government to strengthen market supervision, promoting enterprises to disclose high-quality environmental information, and improving the pricing efficiency of the capital market.

DS-HECK: double-lasso estimation of Heckman selection model

We extend the Heckman (1979) sample selection model by allowing for a large number of controls that are selected using lasso under a sparsity scenario. The standard lasso estimation is known to under-select causing an omitted variable bias in addition to the sample selection bias. We outline the required adjustments needed to restore consistency of lasso-based estimation and inference for vector-valued parameters of interest in such models. The adjustments include double lasso for both the selection equation and main equation and a correction of the variance matrix. We also connect the estimator with results on redundancy of moment conditions. We demonstrate the effect of the adjustments using simulations and we investigate the determinants of female labor market participation and earnings in the US using the new approach. The paper comes with dsheckman, a dedicated Stata command for estimating double-selection Heckman models.

Study on the Impact of Social Capital on Farmers’ Decision-Making Behavior of Adopting Trusteeship Services

The development of sustainable agriculture is an important link in promoting agricultural modernization. As a new sustainable agricultural production model, the promotion effect of agricultural production trust depends on the participation of farmers. Therefore, based on the micro-data of 461 valid questionnaires from farmers in the Heilongjiang Province and the Heckman sample selection model, this study empirically analyzed the impact of social capital on the decision behavior of farmers to adopt custody services from two aspects of adoption behavior and adoption degree. The results showed that social capital had a significant positive impact on the adoption behavior and the degree of adoption of rural households’ trusteeship services. From the perspective of different business scales, for large-scale households, participation in the service promotion activities of agricultural means of production suppliers and trust in the technical information disseminated by the government had a significant positive impact on the adoption of custody services. However, for small farmers, participating in village collective service promotion activities and trusting the service information spread by their neighbors’ relatives and friends had a significant positive impact on trust adoption behavior. Therefore, more attention should be paid to the impact of social capital on farmers’ trust adoption behavior decision making in the future agricultural trust service promotion process to accelerate the promotion of sustainable agricultural development.

Rural electrification and women's empowerment in Côte d’Ivoire

PurposeThis paper assesses the impact of this program on the rural women's employment opportunities using data from the 2015 round of the household's living standard survey (HLSS) of Côte d'Ivoire.Design/methodology/approachIn 2013, in order to improve the living conditions of the rural population, the Ivorian government launched the National Program for rural electrification (PRONER) to electrify all localities with more than 500 inhabitants.FindingsThe results show that PRONER, while reducing the time allocated to performing household chores, increases women's employment through the reallocation of time to full-time paid work in the agricultural and non-agricultural sectors. The authors also find that the allocation of men's time is not affected by this programme. A possible mechanism that would explain such a pro-women effect is the labour-saving technology introduced to home production as an effect of the reform.Research limitations/implicationsAs a limitation, it is important to note that these results were obtained in the specific context of PRONER in Côte d’Ivoire and are not necessarily applicable to rural electrification programmes in other contexts. Furthermore, the choice of other indicators to measure women's empowerment is limited by the quality of the data available. It would be interesting for future research to extend this analysis to include other aspects of women's empowerment and household welfare.Originality/valueThis paper is the first to the author’s knowledge to apply a robust econometric method by combining an inverse probability weighted regression adjustment model with Heckman sample selection method to access a robust causal effect of the PRONER in Côte d'Ivoire.

Food security through crop diversification in Manipur: Application of Heckman Sample Selection Model

The paper demonstrates the household food security of crop diversified farm in the state of Manipur. A study was conducted at College of Post Graduate Studies in Agricultural Sciences at Barapani, Meghalaya of Central Agricultural University, Imphal during 2015–16 to 2017–18 by taking two districts namely; Ukhrul and Thoubal selecting one from each region, viz. hill and valley of the state, respectively. A sample of 200 households was drawn by using probability proportional to size. Heckman Sample Selection model was used to analyze the data. The study found that most of the households diversified their crop enterprises which in turn enhanced their household food security by way of consuming own production or generated income helped to purchase food items. Among the factors, namely socio-economic, technological and institutional factors influenced household's decision to diversify crop in the state while determinants of dietary diversity were the age of the household head, family size, extent of crop diversification, non-farm source of income and agricultural income. Hence, the results were indicative of the importance of crop diversification as a viable option in the state for enhanced food security and income of rural smallholders. Hence, wider awareness on crop diversification for realizing its benefits and improving the nutritional status of households in the state of Manipur was the need of the hour.

A Generalized Heckman Model With Varying Sample Selection Bias and Dispersion Parameters

Many proposals have emerged as alternatives to the Heckman selection model, mainly to address the non-robustness of its normal assumption. The 2001 Medical Expenditure Panel Survey data is often used to illustrate this non-robustness of the Heckman model. In this paper, we propose a generalization of the Heckman sample selection model by allowing the sample selection bias and dispersion parameters to depend on covariates. We show that the non-robustness of the Heckman model may be due to the assumption of the constant sample selection bias parameter rather than the normality assumption. Our proposed methodology allows us to understand which covariates are important to explain the sample selection bias phenomenon rather than to only form conclusions about its presence. We explore the inferential aspects of the maximum likelihood estimators (MLEs) for our proposed generalized Heckman model. More specifically, we show that this model satisfies some regularity conditions such that it ensures consistency and asymptotic normality of the MLEs. Proper score residuals for sample selection models are provided, and model adequacy is addressed. Simulated results are presented to check the finite-sample behavior of the estimators and to verify the consequences of not considering varying sample selection bias and dispersion parameters. We show that the normal assumption for analyzing medical expenditure data is suitable and that the conclusions drawn using our approach are coherent with findings from prior literature. Moreover, we identify which covariates are relevant to explain the presence of sample selection bias in this important dataset.