| Summary: | 碩士 === 淡江大學 === 產業經濟學系碩士班 === 102 === In recent years, obesity has become a widespread prevalence of health problems in many developed countries. However, obesity will not only affect health but also labor market outcomes. Many existing studies of obesity almost universally use BMI as a measure of obesity. In the medical literature, the belief that BMI is an accurate measure of obesity is not always well-founded, because it does not distinguish fat from muscle, bone, and other lean body mass.
This study, hence, uses three measures of obesity--BMI, percent body fat and waist circumference--to examine the impact of body size on employment. The data come from three waves of National Health and Nutrition Examination Survey (NHANES), including the 1999-2000, 2001-2002 and 2003-2004 surveys, since these three waves of data have those three measures of obesity. By making flexible distribution assumption, it uses the seminonparametric model and seminonparametric estimation of bivariate binary-choice model. To take the potential endogeneity of BMI, percent body fat and waist circumference into account, it uses regional prevalence rate of obesity as our instrumental variable and uses Control function approach to tackle this problem.
The results of seminonparametric model indicate an inverted U-shaped curve for the effects of BMI, percent body fat or waist circumference on employment for men, especially significant in the waist circumference model. On the other hand, the results show a negative linear effect for the impact of BMI, percent body fat or waist circumference on employment for women, and they are all significant. The results of seminonparametric estimation of bivariate binary-choice model indicate that both men and women whose BMI is greater than or equal to 30 have significantly lower probability of employment. However, we only find significantly negative impact of percent body fat obesity and central obesity on employment among women. In the three measures of obesity, central obesity has the greatest impact on employment for woman.
This study, furthermore, attempts to use obesity-related diseases--hypertension and diabetes--as control variables. To take the potential endogeneity of hypertension and diabetes into account, it uses regional prevalence rate of hypertension and diabetes as instrumental variables, and it, again, uses Control function approach to tackle this problem. After controlling for those two health conditions, it finds that the impact of obesity on employment is slightly weakened, in general.
If we only use BMI as a measure of obesity, obesity will have the negative impact on labor market outcomes for both men and women. However, if we further consider the impact of percent body fat or waist circumference on employment, we not only capture an inverted U-shaped curve for the effects of waist circumference on employment for men, but also find that obesity will negatively affect women relatively more than men.
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