Twin births are often construed as a natural experiment in the social and natural sciences on the premise that the occurrence of twins is quasi-random. We present new population-level evidence that challenges this premise. Using individual data for 17 million births in 72 countries, we...

Twin births are often used to instrument fertility to address (negative) selection of women into fertility. However recent work shows positive selection of women into twin birth. Thus, while OLS estimates will tend to be downward biased, twin-IV estimates will tend to be upward biased. This is...

The Nigerian civil war of 1967-70 was precipitated by secession of the Igbo-dominated south-eastern region to create the state of Biafra. It was the first civil war in Africa, the predecessor of many. We investigate the legacies of this war four decades later. Using variation across ethnicity...

A recent literature highlights the uncertainty concerning whether economic growth has any causal protective effect on health and survival. But equal rates of growth often deliver unequal rates of poverty reduction and absolute deprivation is more clearly relevant. Using state-level panel data...

We exploit exogenous variation in the risk of waterborne disease created by implementation of a major water reform in Mexico in 1991 to investigate impacts of infant exposure on indicators of cognitive development and academic achievement in late childhood. We estimate that a one standard...

This paper investigates the sensitivity of the intergenerational transmission of health to exogenous changes in income, education and public health, changes that are often delivered by economic growth. It uses individual survey data on 2.24 million children born to 600000 mothers during...

IVF allows women to delay birth and pursue careers, but IVF massively increases the risk of twin birth. There is limited evidence of how having twins influences women's post-birth careers. We investigate this, leveraging a single embryo transfer (SET) mandate implemented in Sweden in 2003,...

We investigate the importance of subjective expectations of returns to and effort costs of the two main investments that mothers make in newborns: breastfeeding and stimulation. We find heterogeneity across mothers in expected effort costs and expected returns for outcomes in the cognitive,...

In this study we examine the passage of a reform to in-vitro fertilization (IVF) procedures in Sweden in 2003. Following publication of medical evidence showing that pregnancy success rates could be maintained using single rather than multiple embryo transfers, the single embryo transfer (SET)...

We analyze long-term impacts of the 1967-1970 Nigerian Civil War, providing the first evidence of intergenerational impacts. Women exposed to the war in their growing years exhibit reduced adult stature, increased likelihood of being overweight, earlier age at first birth, and lower educational...