• Journal of the Korean Data and Information Science Society
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• v.28 no.5
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• pp.1099-1107
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• 2017

In this study, we analyzed the determinants of wages of college graduates by using the data of "2014 Graduates Occupational Mobility Survey" conducted by Korea Employment Information Service. In general, wages contain two complex pieces of information about whether an individual is employed and the size of the wage. However, in many previous researches on wage determinants, sample selection bias tends to be generated by performing linear regression analysis using only information on wage size. We used the Heckman sample selection models for analysis to overcome this problem. The main results are summarized as follows. First, the validity of the Heckman's sample selection model is statistically significant. Male is significantly higher in both job probability and wage than female. As age increases and parents' income increases, both the probability of employment and the size of wages are higher. Finally, as the university satisfaction increases and the number of certifications acquired increased, both the probability of employment and the wage tends to increase.

• Journal of the Korean Data and Information Science Society
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• v.28 no.5
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• pp.1077-1085
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• 2017

In this study, we have found the major factors which affect Korean women's wage analysing the data provided by 2015 Korea Labor Panel Survey (KLIPS). In general, wage data is difficult to analyze because random sampling is infeasible. Heckman sample selection model is the most widely used method for analysing the data with sample selection. Heckman proposed two kinds of selection models: the one is the model with maximum likelihood method and the other is the Heckman two stage model. Heckman two stage model is known to be robust to the normal assumption of bivariate error terms. Recently, Marchenko and Genton (2012) proposed the Heckman selectiont model which generalizes the Heckman two stage model and concluded that Heckman selection-t model is more robust to the error assumptions. Employing the two models, we carried out the analysis of the data and we compared those results.

• Journal of the Korean Data and Information Science Society
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• v.27 no.5
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• pp.1317-1325
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• 2016

The purpose of this paper is to explain the factors affecting the wage of the vocational high school graduates. We particularly examine the effectiveness of controlling sample selection bias by employing the Tobit model and Heckman sample selection model. The major results are as follows. First it is shown that the Tobit model and Heckman sample selection model controlling sample selection bias is statistically significant. Hence all the independent variables seem to be statistically consistent with the theoretical model. Second, gender was statistically significant, both in the probability of employment and the wage. Third, the employment probability and wage of Maester high school graduates were shown to be high compared to all other graduates. Fourth, the higher parent's income, the higher are both the employment probability and the wage. Finally, parents education level, high school grade, satisfaction, and a number of licenses were found to be statistically significant, both in the probability of employment and wages.

• The Journal of Fisheries Business Administration
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• v.55 no.1
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• pp.37-53
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• 2024

In the post-COVID-19, the food industry is rapidly reshaping its market structure toward online distribution. Rapid delivery system driven by large distribution platforms has ushered in an era of online distribution of fresh seafood that was previously limited. This study surveyed 1,000 consumers nationwide to determine their online seafood purchasing behaviors. The research methodology used factor analysis of consumer lifestyle and Heckman's ordered probit sample-selection model. The main results of the analysis are as follows. First, quality, freshness, selling price, product reviews from other buyers, and convenience are particularly important considerations when consumers purchase seafood from online shopping. Second, online retailers and the government must prepare measures to expand seafood consumption by considering household characteristics and consumer lifestyles. Third, it was analyzed that consumers trust the quality and safety of seafood distributed online platforms. It is not possible to provide purchase incentives to consumers who consider value consumption important, so improvement measures are needed. The results of this study are expected to provide implications on consumer preferences to online platforms, seafood companies, and producers, and can be used to establish future marketing strategies.

• The Korean Journal of Applied Statistics
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• v.31 no.6
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• pp.733-749
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• 2018

Sample selection arises as a result of the partial observability of the outcome of interest in a study. Heckman introduced a sample selection model to analyze such data and proposed a full maximum likelihood estimation method under the assumption of normality. Recently sample selection models for binomial and Poisson response variables have been proposed. Based on the theory of symmetry-modulated distribution, we extend these to a model for overdispersed count data. This type of data with no sample selection is often modeled using negative binomial distribution. Hence we propose a sample selection model for overdispersed count data using the negative binomial distribution. A real data application is employed. Simulation studies reveal that our estimation method based on profile log-likelihood is stable.

• Journal of Korean Society of Rural Planning
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• v.27 no.3
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• pp.47-56
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• 2021

The purpose of this study is to identify the determinants of local farmers' participation and acceptance level in traditional agricultural technology conservation activities, using on the traditional agricultural water utilization system in Uiseong designated as Korea's important agricultural heritage system No. 10. The Heckman sample selection model was used to solve the selection bias. The results show that as the interest in the conservation of the agricultural ecological and environment is high, as the traditional agricultural system in Uiseong is used, as the cultivation area of paddy field increased, and as the age 50s or older, the willingness to participate in conservation activities increased. The results also indicate that as the experience of participating in the conservation of the agricultural ecological and environment and the hours of education are increased, the knowledge of the traditional agricultural system in Uiseong is low, and as the cultivation area of paddy field decreased, the acceptance time for conservation activities increased. The results of this study may contribute to government's policy for traditional agricultural technology conservation.

• Informatization Policy
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• v.27 no.1
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• pp.36-54
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• 2020

This study empirically analyzes the impact of digital divide between digital device usage motivation and operational skills on online political participation. The analysis was performed using the National Information Society Agency's 2018 digital divide survey data from September to December 2018 and applying the Heckman selection model to control the sample selection bias that may occur between internet users and non-users. The result shows the gap in motivation and device operational skills of individual citizens using digital devices has significant impact on online political participation. In socio-economic terms, it shows the age, education level and regional factors also have significant impact on online political participation, while gender and income levels do not. This study holds significance in that there are different patterns of digital divide between digital devices, identifying the motivation to use a digital device as an important factor for mobile device users, and the device operational skills, for personal computer users.

• International Journal of Human Ecology
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• v.4 no.2
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• pp.77-87
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• 2003

This paper tried to construct statistical and econometric models on the basis of economic theory in order to discuss the issue of statistical efficiency and unbiasedness including the sample selection bias correcting problem. Comparative analytical tool were one stage Tobit of Maximum Likelihood estimation and Heckman's two-step Tobit of Ordinary Least Squares. The results showed that the adequacy of model for the analysis on demand and choice, we believe that there is no big difference in explanatory variables between the first selection model and the second linear probability model. Since the Lambda, the self- selectivity correction factor, in the Type II Tobit is not statistically significant, there is no self-selectivity in the Type II Tobit model, indicating that Type I Tobit model would give us better explanation in the demand for and choice which is less complicated statistical method rather than type II model.

• Health Policy and Management
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• v.15 no.2
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• pp.16-36
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• 2005

Due to the existence of asymmetry of information between doctor and patient, it has been believed that doctor might affect patient's decision making process of purchasing medical care. Based on this notion, doctor's reimbursement method has been suggested as an effective policy device of improving efficiency of patient's medical care use by way of its affecting doctor's practice pattern. By using the Community Tracking Study (CTS) household and physician data set, which includes not only various information on patient's medical care use, but doctor's practice arrangements and sources of practice revenue, this paper investigates the effect of community doctor's characteristics of reimbursement method on community patient's medical care use under the control of patient's socio-demographic characteristics and community doctor's practice type. In the process of estimating econometric model, the endogeneity problem of individual health insurance purchase was corrected by using 2818. And due to the existence of sample selection problem, Heckman's two-step estimation method was used for strengthen the robustness of estimation which was adversely affected by sample selection problem The empirical results show that as the average value of community doctor's portion of practice revenue determined by prospective method out of total revenue increases, the community patient's total out-of-pocket medical cost decreases. This results suggest, as doctor's practice revenues are mainly determined by prospective method, such as capitation, doctors would be more conscious about practice cost, which might affect doctor's practice pattern and by which his/her patient's use of medical care would decrease.

• Environmental and Resource Economics Review
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• v.31 no.1
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• pp.1-30
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• 2022

This study is to investigate consumers' acceptance and their willingness to pay for clothes made of materials with low microplastic emissions as an alternative to synthetic fibers made of plastics by applying the contingent valuation method. A nationwide web-based survey was conducted for 1,052 respondents proportional to region, age, and gender during February 2021. More than 75% of the sample expressed intentions to purchase microplastic emission-reducing clothing instead of synthetic fiber clothing, and more than 80% of them have stated their willingness to pay for additional prices. A variation of Heckman's sample selection model was adopted to estimate factors affecting respondents' intentions to pay for additional prices, in which the probit model of intentions to purchase the clothing with alternative materials was used as a sample selection equation. While respondents were sensitive to the amounts of price increases suggested in the CV scenario, they expressed high acceptance and preferences for eco-friendly materials regardless of the microplastic emission-reducing levels. Consumers in the circular economy were willing to pay for the range of 41,000 to 51,000 won for a pair of clothing made with microplastic emission-reducing materials. In addition, as the microplastic emission-reducing rate has increased from 50% to 80%, the willingness to pay estimates were also significantly increased, ranging from 41,000~50,500 to 42,000~51,700 won.