Dinand Webbink

We analyse the causal effect of education on starting and quitting smoking, using longitudinal data of Australian twins. We take into account the endogeneity of education, censoring of smoking durations and the timing of starting smoking versus that of completing education by using the flexible Mixed Proportional Hazard (MPH) specification. Unobserved effects in the specification are assumed to be twin specific and possibly correlated with completed education years. In addition, we use various unique control indicators reflecting the discounting behaviour of individuals that may affect both the smoking decision and the number of education years. In contrast to previous studies in our model specification, differences in the number of education years cannot explain differences in smoking behaviour at young ages. We find one additional year of education to reduce the duration of smoking with 9 months, but no significant effect of education on starting smoking. The effect of education on quitting smoking largely confines to male twins. This suggests that education policies that succeed in raising the level of education may improve public health through an increase of smoking cessation, but are not effective in preventing smoking at young ages.

This study investigates the impact of two local calamities-an explosion at a firework factory in the city of Enschede on 13 May and a fire at a discotheque on 1 January 2001 during a New Years Eve party in the town of Volendam-on the educational achievement of children at the end of their primary education. Based on a quasi-experimental design with both control groups and pre-tests, we found that in the three years following the two tragedies, the test scores of girls in those areas closest to the events were on average 0.2 standard deviations lower. This corresponds to a downward shift in the distribution of girls' test scores. Boys' test scores, meanwhile, were not significantly affected by the disasters, and nor were the scores of pupils from nearby areas. In the three years following the calamities, girls' test scores in one of the areas (Volendam) have slowly recovered, although they remain well below their pre-event level.

This paper investigates the question whether crime reduces investment in human capital or whether education reduces criminal activity by using fixed effect estimation on data of Australian twins. The study takes genetic and socio-economic factors shared by the twins into account. We find that early arrests (before the age of 18) have a strong effect on human capital accumulation. In addition, we find that education decreases crime. However, controlling for early arrests and early behaviour problems reduces the estimated effect of human capital on crime to less than on third of the previously estimated association. From this, we conclude that the strong association between human capital and crime is mainly driven by the effect of early criminal behaviour on educational attainment. The strong detrimental effects of early criminal behaviour become also transparent if we consider the estimated effects of early arrests on three measures of crime. We also find large effects of early criminal behaviour on participation in crime later on. This suggests that programs that succeed in preventing early criminal behaviour might yield high social and private returns.

This paper estimates the longer-term effects of childhood conduct disorder on human capital accumulation and violent and criminal behaviour later in life using data of Australian twins. We measure conduct disorder with a rich set of indicators based on diagnostic criteria from psychiatry (e.g., aggression to people and animals, destruction of property, deceitfulness or theft, and/or serious violations of rules). Using ordinary least squares (OLS) and twin fixed effects (FE) estimation approaches, we find that early (pre-18) conduct disorder problems significantly affect both human capital accumulation and violent and criminal behaviour over the life course. For instance, within pairs of identical twins we find that conduct disorder reduces the probability of high school graduation with 4 to 13 percent points and increases the probability of being arrested with 7 to 16 percent points. Robustness checks suggest that these estimates may be lower bounds of the true effects of conduct disorder. In addition, we find that conduct disorder is more deleterious if these behaviours occur earlier in life. We conclude that childhood mental health problems have high human and financial costs for families and society at large. Effective treatments early in life might yield high returns.

This paper analyses the causal effect of education on the probability of being overweight by using longitudinal data of Australian identical twins. The data include self-reported and clinical measures of body size. The prevalence of overweight and obesity is growing rapidly in many countries. Education policies might be important for reducing this increase. Our cross-sectional estimates confirm the well-known negative association between education and the probability of being overweight. For men we find that education also reduces the probability of being overweight within pairs of identical twins. The estimated effect of education on overweight status increases with age. Remarkably, for women we find no negative effect of education on body size when fixed family effects are taken into account. Identical twin sisters that differ in educational attainment do not systematically differ in body size. This finding is robust to differences in employment and number of children.