This study could not have been completed without the help of the following people: in Washington-Maria Otero and Mohini Malhotra; in La Paz-Miguel Taborga, Sergio Ortiz and Paola Barragan. Particular thanks are due to Pancho Otero for accepting my intrusions with great warmth in the middle of an exceptionally hectic fortnight in late April 1993, and to the brave team of enumerators-Felipe Santos, Juan Charles Ascarrus, Waldo Carpio, Leopoldo Molinedo, Guadalupe Calderon, Maria Luisa Rea Machado and their supervisor, Bernardo Santa Maria-for carrying out a strenuous task with exceptional good humour and professionalism.