Family size and child outcomes: Is there really no trade-off?

We study the impact of family size on intermediate and long-term outcomes using twin births as an exogenous source of variation in family size in an unusually rich dataset. Similar to recent studies, we find no evidence of a causal effect on long-term outcomes and show that not taking selection effects into account will likely overstate the effects. We do, however, find a small but significant negative impact of family size on grades in compulsory and secondary school among children who are likely to be vulnerable to further restrictions on parental investments. (C) 2009 Elsevier B.V. All rights reserved.