Incomplete contracts and the boundaries of the multinational firm. Nathan Nunn, October 2012, Paper. "Using data on U.S. intra-firm and arm’s-length imports for 5,705 products imported from 220 countries, we examine the determinants of the share of U.S. imports that are intra-firm. We examine two predictions that arise from Antràs (2003), Antràs & Helpman (2008) and Antràs & Helpman (2004). First, we find that, consistent with the implicit logic of Antràs (2003) and the explicit predictions of Antràs & Helpman (2008), vertical integration is increasing in the importance of non-contractible headquarter inputs..." Link