Following in Your Father's Footsteps: A Note on the Intergenerational Transmission of Income between Twin Fathers and their Sons

We provide the first twin-based estimates of the intergenerational transmission of income between fathers and sons. Using Swedish register data on the income of monozygotic twin fathers and their sons, we are able to control for unobserved endowments at the twin-pair level when estimating the intergenerational relationship. We find a cross-sectional intergenerational income elasticity of 0.276, while our twin-based intergenerational income elasticity is 0.12. This is close to the estimate of 0.10 found by Björklund et al. (2006) using an adoption design. This suggests that at most half of the income transmission can be given a causal interpretation.twins, income, intergenerational transmission, intergenerational mobility

Mothers Do Matter: New Evidence on the Effect of Parents' Schooling on Children's Schooling Using Swedish Twin Data

Behrman and Rosenzweig (2002) used data on a small sample of MZ (monozygotic, identical) twin parents and their children to show that father's schooling is more important than mother's schooling for children's schooling in the U.S. Recent studies based on much larger samples of twins from registry data in Scandinavian countries reach similar conclusions. Most of these studies, however, are unable to distinguish between MZ and DZ (dizygotic, fraternal) twins. Using data from the Swedish Twin Registry, we replicate the finding that father's schooling matters more than mother's schooling in a combined sample of MZ and DZ twin parents. In contrast, results based on MZ twin parents show that mother's schooling matters at least as much as father's schooling for children's schooling. We also estimate the effect of parents' schooling separately by child gender and find this effect to be entirely driven by the impact of mother's schooling on daughter's schooling. Our results show that (1) it is vital to have zygosity information to estimate causal intergenerational effects and (2) the conclusions reached by Behrman and Rosenzweig (2002) for the U.S. do not apply in Sweden.twins, twin-fixed effects, schooling, intergenerational mobility

Do More-Schooled Women have Fewer Children and Delay Childbearing? Evidence from a Sample of U.S. Twins

Using data on MZ (monozygotic, identical) female twins from the Minnesota Twin Registry, we estimate the causal effect of schooling on completed fertility, probability of being childless and age at first birth, using the within-MZ twins methodology. We find strong cross-sectional associations between schooling and the fertility outcomes and some evidence that more schooling causes women to have fewer children and delay childbearing, though not to the extent that interpreting cross-sectional associations as causal would imply. Our conclusions are robust when taking account of (1) endogenous within-twin pair schooling differences due to reverse causality and (2) measurement error in schooling. We also investigate possible mechanisms and find that the effect of women’s schooling on completed fertility is not mediated through husband’s schooling but rather through age at first marriage

Mothers do matter: New evidence on the effect of parents' schooling on children's schooling using Swedish twin data

Behrman and Rosenzweig (2002) used data on a small sample of MZ (monozygotic, identical) twin parents and their children to show that father's schooling is more important than mother's schooling for children's schooling in the U.S. Recent studies based on much larger samples of twins from registry data in Scandinavian countries reach similar conclusions. Most of these studies, however, are unable to distinguish between MZ and DZ (dizygotic, fraternal) twins. Using data from the Swedish Twin Registry, we replicate the finding that father's schooling matters more than mother's schooling in a combined sample of MZ and DZ twin parents. In contrast, results based on MZ twin parents show that mother's schooling matters at least as much as father's schooling for children's schooling. We also estimate the effect of parents' schooling separately by child gender and find this effect to be entirely driven by the impact of mother's schooling on daughter's schooling. Our results show that (1) it is vital to have zygosity information to estimate causal intergenerational effects and (2) the conclusions reached by Behrman and Rosenzweig (2002) for the U.S. do not apply in Sweden

Following in your father's footsteps: A note on the intergenerational transmission of income between twin fathers and their sons

We provide the first twin-based estimates of the intergenerational transmission of income between fathers and sons. Using Swedish register data on the income of monozygotic twin fathers and their sons, we are able to control for unobserved endowments at the twin-pair level when estimating the intergenerational relationship. We find a cross-sectional intergenerational income elasticity of 0.276, while our twin-based intergenerational income elasticity is 0.12. This is close to the estimate of 0.10 found by Björklund et al. (2006) using an adoption design. This suggests that at most half of the income transmission can be given a causal interpretation

Schooling has Smaller or Insignificant Effects on Adult Health in the US than Suggested by Cross-Sectional Associations: New Estimates Using Relatively Large Samples of Identical Twins

Adult health outcomes and health behaviors generally are strongly associated with schooling attainment. But such associations do not necessarily imply that schooling has causal effects on health outcomes and behaviors of the magnitudes of the associations. Schooling may be proxying for unobserved factors that are related to genetics and family background. Recently several studies have used within-identical (monozygotic, MZ) twins methods to control for those unobserved factors that are shared completely by identical twins. Estimates based on relatively small samples for the US, as well as some larger samples for other countries, suggest that causal impacts of schooling on health outcomes and behaviors are insignificant or much smaller than suggested by cross-sectional associations. This study contributes new estimates of cross-sectional associations and within-MZ causal effects of twins using three relatively large US samples: Mid-Atlantic Twin Registry, Minnesota Twin Registry and NAS-NRC Twin Registry of WWII Military Veterans. The estimates suggest that schooling is significantly associated with numerous health outcomes and behaviors in the US. However if within-MZ twins estimators are used to control for unobserved factors, there is no causal relationship between schooling and better health behaviors. There is some evidence that more schooling causally affects self-reported health and overweight status, net of unobservable cofounders, though not to the extent that cross-sectional associations suggest. Finally, spousal schooling is associated with better health outcomes and behaviors, but there is no evidence of any causal effect

The Effect of Degree Attainment on Arrests: Evidence from a Randomized Social Experiment

We examine the effect of educational attainment on criminal behavior using random assignment into Job Corps (JC) – the United States' largest education and vocational training program for disadvantaged youth – as a source of exogenous variability in educational attainment. We allow such random assignment to violate the exclusion restriction when used as an instrument by employing nonparametric bounds. The attainment of a degree is estimated to reduce arrest rates by at most 11.8 percentage points (about 32.6%). We also find suggestive evidence that the effects may be larger for males relative to females, and larger for black males relative to white males. Remarkably, our 95 percent confidence intervals on the causal effect of education on arrests are very similar to the corresponding confidence intervals on the same effect from studies exploiting changes in compulsory schooling laws as an instrumental variable in the estimation of the effect of education on arrest rates (e.g., Lochner and Moretti, 2004)

The Impact of BMI on Mental Health: Further Evidence from Genetic Markers

We examine the relationship between body mass index (BMI) and mental health for young adults and elderly individuals using data from the National Longitudinal Study of Adolescent Health and the Health & Retirement Study. While ordinary least squares (OLS) estimates show that BMI is significantly associated with worse mental health in both young adulthood and old age, they are likely to be confounded by (i) unobserved factors that affect both BMI and mental health and (ii) reverse causality. To tackle confounding, we take two complementary approaches. First, we use a polygenic score for BMI as an instrumental variable (IV) and adjust for polygenic scores for other factors that may invalidate this IV. The IV estimates indicate that there is no statistically significant relationship between BMI and mental health for young adults, whereas there is a positive and statistically significant relationship for the elderly. Moreover, we show that IV estimates likely have to be interpreted as identifying a weighted average of effects of BMI on mental health mostly for individuals on the upper quantiles of the BMI distribution. Given potential remaining concerns about the validity of the IV, our second approach is to consider it an “imperfect” IV and estimate an upper bound on the average treatment effect for the corresponding population following Nevo & Rosen (2012). The estimated upper bounds reinforce the conclusions from the IV estimates: they show little evidence of a detrimental effect of BMI on mental health for young adults while being consistent with an economically meaningful effect for elderly individuals. Lastly, we explore some of the potential channels through which BMI may affect mental health for the elderly

Mental Health, Schooling Attainment and Polygenic Scores: Are There Significant Gene-Environment Associations?

We estimate associations between a polygenic score (PGS) for depressive symptoms, schooling attainment and genetic-environmental (GxE) associations with depressive symptoms and depression for 29 years old in the National Longitudinal Study of Adolescent Health (Add Health) and 53 years old in the Wisconsin Longitudinal Study (WLS). We find some suggestive evidence that the association of the PGS with mental health is lower for more-schooled older individuals in the WLS, but no evidence in Add Health. Quantile regression estimates also show that in the WLS the GxE associations are statistically significant only in the upper parts of the conditional depressive symptoms score distribution. We assess the robustness of the OLS results to possible omitted variable bias by estimating sibling fixed-effect regressions. The sibling fixed-effect results must be qualified, in part due to low statistical power. However, they show that college education is associated with fewer depressive symptoms in both datasets

Genetic Risks, Adolescent Health and Schooling Attainment

We provide new evidence on the effect of adolescent health behaviors/outcomes (obesity, depression, smoking, and attention deficit hyperactivity disorder (ADHD)) on schooling attainment using the National Longitudinal Study of Adolescent to Adult Health. We take two different approaches to deal with omitted variable bias and reverse causality. Our first approach attends to the issue of reverse causality by using health polygenic scores (PGSs) as proxies for actual adolescent health. Second, we estimate the effect of adolescent health using sibling fixed-effects models that control for unmeasured genetic and family factors shared by siblings. We use the PGSs as additional controls in the sibling fixed-effects models to reduce concerns about residual confounding from sibling-specific genetic differences. We find consistent evidence across both approaches that being genetically predisposed to smoking and smoking regularly in adolescence reduces schooling attainment. We find mixed evidence for ADHD. Our estimates suggest that having a high genetic risk for ADHD reduces grades of schooling, but we do not find any statistically significant negative effects of ADHD on grades of schooling. Finally, results from both approaches show no consistent evidence for a detrimental effect of obesity or depression on schooling attainment