Previously, he was associate professor of economics at Stanford University's Graduate School of Business. An expert on international political economy, he has focused mainly on international trade and its relationship with economic development. Most recently, he has published research on the relationship between openness to trade and economic growth, as well as on the effect of an open world-trade regime on incentives for geographic regions to secede. His other areas of recent focus include a study linking ethnic, religious and linguistic diversity with economic variables; a study evaluating the economic costs and benefits of political borders; and two studies evaluating the relationship between international trade and the rise and fall of industries.