Δοκίμια στην οικονομική της παχυσαρκίας

Abstract

Recently economists pay a lot of attention on the analysis of obesity since the prevalence of obesity is widespread. This dissertation examines four research questions associated with the Economics of Obesity. Specifically, with respect to the first empirical chapter, obesity is modeled as a dynamic stochastic process and patterns of obesity experiences are investigated. Longitudinal data from US adults (NLSY79) and appropriate dynamic models were utilized. Strong persistence was detected in obesity and the body-mass-index (BMI), albeit with different properties. While controlling for initial conditions (early-life endowments and family background), the identified obesity persistence was decomposed into unobserved heterogeneity and genuine state dependence. Results from the sensitivity analysis show that obesity has a lasting effect, which however is not stable across the BMI distribution, exhibiting a steeper decline at BMI levels close to the clinical definition of obesity. Moreover, in the same chapter, we also explore the dynamic behavior of alternative fatness states (normal weight, overweight and obese) and the corresponding persistence, utilizing appropriated dynamic ordered models. Relevant policy implications are discussed. The second chapter investigates the dynamic patterns the duration of obesity and identifies the determinants of obesity-spell exits and re-entries. We utilize longitudinal data from the NLSY79, as before. Non-parametric techniques are applied to investigate the relationship between exit from obesity and spell duration. Multivariate discrete hazard models are also estimated, taking into account duration dependence and observed and time-invariant unobserved heterogeneity. In all cases, the probability of exiting obesity is inversely related to the duration of the obesity spell. Without controlling for unobserved heterogeneity, the probability of exit after one wave in obesity is 31.5 per cent; it is reduced to 3.8 per cent after seven or more waves. When time-invariant unobserved heterogeneity is taken into account, the estimated probabilities are slightly larger and broadly similar (36.8 and 10.3, respectively), which suggests that the identified negative duration dependence is not primarily due to composition effects. The obtained results indicate that public health interventions targeting the newly obese may be particularly effective at reducing incidence of long durations of obesity. In the third empirical chapter we investigate obese/non-obese wage differentials using data for white individuals from the 2000 wave of the NLSY79. Based on the results from the previous chapters, we assume that obesity is a rather permanent characteristic that associated with relatively small mobility. Hence, typical Oaxaca-Blinder wage decompositions could be applied in order to identify the proportion of the observed gender-specific wage differential between obese and non-obese. Based on numerous specifications and alternative sub-samples the results provide strong evidence for the existence of wage differentials in favor of non-obese individuals, which can be mostly explained by differences in early human capital investments and especially schooling investments. Finally, an attempt was made to identify the determinants of body-weight in Greece, utilizing individual-level data from the National Health Survey of 2009. BMI is treated as both, a cardinal and an ordinal measure of body-weight, while different estimation techniques are applied (OLS, ordered probit and unconditional quantile regressions). We employ a wide range of demographic, socio-economic, lifestyle, health-related and regional characteristics. The unconditional quantile regression estimates indicate that the impact of several correlates across the BMI distribution is distinctive. This differentiation concerns the effects of age, education, family income, physical activity, employment status, smoking, health-related impairments and regional characteristics. Thus, examining the entire BMI distribution and targeting specific segments of the Greek population can improve the efficiency of public health policies against obesity.