interviews were conducted with over $1,000$ strnet$$vendors in the city of Puebla, Mexico, in order$$to study the factors influencing vendors'incomes$($World Development, February $1998).$ Vendors$$were defined as individuals working in the street,$$and included vendors with carts and stands on$$wheels and excluded beggars, drug dealers, and$$prostitutes$.$ The researchers collected data on gender,$$age$,$ hours worked per day, annual earnings,$$and education level. A subset of these data appears$$in the accompanying table.