foreign direct investment, preferential trade agreements, gravity model 1 | INTRODUCTION We estimate the potential impact of preferential trade agreements (PTAs)-and other bilateral policies that affect trade and investment-on the bilateral FDI stocks and flows between the countries signing these agreements. Our key results are based on a structural gravity model of FDI that is applied to bilateral FDI data from UNCTAD (2014), while controlling for the presence, heterogeneity and depth of preferential trade agreements (PTAs), and other time-varying bilateral policies. Starting in the 1990s, the world economy has experienced a large increase in the number of PTAs, and also in their 'depth'-measured by the number of their operative provisions. 1 While stimulating bilateral trade is the main focus of most PTAs, recent preferential trade agreements increasingly contain provisions on bilateral investment between member states. However, the impact of PTAs on the magnitude of foreign direct investments is not straightforward. Trade and FDI can either complement or substitute each other, depending on the investment motivation (i.e., horizontal and vertical), the specific industry and on the way in which the FDI provisions are shaped in the PTA. From a theoretical point of view, horizontal FDI-where firms replicate domestic activities in a foreign country-is associated with FDI substituting for trade. Thus, in the presence of horizontal FDI, PTAs are expected to decrease FDI flows. On the other hand, vertical FDI-where firms split activities between different geographical regions-creates a complementary relationship between trade, PTAs and FDI (cf. Markusen, 2002). More recently, and, in part, due to the expansion and complexity of global value chains (GVCs), other motives for FDI have been identified. For instance, export-platform FDI where MNEs produce to export to third markets (Ekholm, Forslid, & Markusen, 2007; Hanson, Mataloni, & Slaughter, 2005). Yeaple (2003) classifies mixed FDI motives as 'complex FDI'. Baldwin and Okubo 1 + jit 1 + ijt .