Farbmacher, Helmut; Guber, Raphael; Vikström, Johan - 2016
Twin births are an important instrumental variable for the endogenous fertility decision. However, in many economic … settings, twins are not exogenous as dizygotic twinning is known to be correlated with maternal characteristics and fertility … administrative data from Sweden and US census data and show that the usual twin instrument is not only related to observed but also …