I describe multinational corporations’ (MNCs’) motivations for engaging in foreign direct investment (FDI) rather than other forms of internationalisation. When it comes to understanding the underlying determinants of an investment, some of the issues presented by FDI studies relying on high levels of aggregated FDI measures are caused by aggregation, and others are driven by data. There are gains from disaggregation in existing studies of both FDI and global supply chains and benefits for policymakers of pursuing and promoting such an approach.