"January 1998 marked the 25th anniversary of the Supreme Court decision in Roe v Wade (410 US 113) that legalized abortion nationwide. Since that decision, abortion policy has remained one of the most contentious of issues in American politics; as recently as 1992, the Supreme Court came within 1 vote of reversing the Roe decision (Planned Parenthood of Southeastern Pennsylvania v Casey, 505 US 833). Although positions are largely developed on philosophical and moral grounds, the empirical magnitude of the effect of legal access to abortion is both important and rarely studied. Our purpose in this article is to estimate the effects of abortion legalization on fertility rates in the United States."