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,...

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 more than 18 million births (more than 500,000...

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)...

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...

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...

The introduction of prenatal sex-detection technologies in India has led to a phenomenal increase in abortion of female fetuses. We investigate their impact on son-biased fertility stopping behavior, parental investments in girls relative to boys, and the relative chances of girls surviving...