Puerto Rico experienced one of the world's most rapid growth rates in both GDP per capita and labor productivity - a performance that puts it into the same league as Japan, South Korea, Taiwan and Singapore. Moreover, Puerto Rico significantly narrowed the productivity gap between itself and the United States. Special circumstances played a role in its development, including unrestricted emigration to the mainland, generous federal transfer payments, and special tax incentives for investment. But our analysis suggests that even without these advantages annual growth in GDP per capita would have averaged 3.8% over 1950-90, instead of its actual rate of 4.2%. Copyright (C) 1996 Elsevier Science Ltd