We examine the empirical role of different explanations for the lack of capital flows from rich to poor countries—the “Lucas Paradox.” The theoretical explanations include cross-country differences in fundamentals affecting productivity, and capital market imperfections. We show that during 1970–2000, low institutional quality is the leading explanation. Improving Peru’s institutional quality to Australia’s level implies a quadrupling of foreign investment. Recent studies emphasize the role of institutions for achieving higher levels of income but remain silent on the specific mechanisms.