It is contended that the informal sector of the urban labor market is not the major point of entry for fresh migrants from rural areas and that large variations in earning exist within it. A disproportionately large number of informal sector workers are: 1) very young or very old; 2) female; 3) limited in education; and 4) not primary household earners. Earnings are low in the informal sector partly because of the selective factors affecting the type of labor found in this sector. There is, however, a wide diversity of earnings in the sector and within important components (the self-employed and those in the tertiary activities). The cumulative effect of this critical examination suggests discarding of the popular myth that great masses of low income earners can be found in particular pockets of the urban economy. The migration function implicit in probabilistic job search models exaggerates the volume of migration to the urban market and underplays the role of actual economic performance in constraining migration. Other studies of movements of income and employment over time are required for different types of urban markets, and their results must be considered by government policymakers. Economic and demographic data are included.