In recent decades, Mexico has experienced rapid and drastic demographic, economic and sociocultural changes, which have modified both the conditions of life and the population structure. The Mexican government has made great efforts to improve education, accommodation, hygiene and food quality, and to control tropical diseases (UNDP, 1990). In 1960 the under five mortality rate was 140 per thousand; in 1988 it was 68 per thousand. In 1981 the percentage of one-year-old children with at least one disease was 50; in 1988 it was 75. The adult illiteracy rate fell from 26% in 1970 to 10% in 1985. This process of national development has been slowed by the other changes that are occurring. One such, with far-reaching effects, is the considerable migration to urban from rural areas: the urban population increased from 51% in 1960 to 71% in 1988. This has led to rapid growth of suburban areas in Mexico City, Vera Cruz, Guadalajara and other large towns (indeed, Guadalajara has a population density of 10286 per square km), where year by year the living conditions have deteriorated, become less acceptable, and less controllable. As a generalisation it seems that the worse the antecedent rural environment of the migrants, the worse the condition of their suburban settlements.

A second major problem is the worsening condition of some rural populations, among them the traditional Indian tribes or communities. Their situation has deteriorated through cultural, linguistic, historical and political isolation much more than through deterioration of their geographical environment.