[Migration toward medium-sized cities. Profound regional transformations].

Significant changes have occurred over the past two decades in the volume intensity direction and modalities of internal migration in Mexico. Interstate migration for example has increased greatly. The number of persons living in a state different from that of their birth grew from 7.5 million in 1970 to 15.4 million in 1990 equivalent to 14.5% and 18.1% of the population respectively. The growing volume and intensity of interstate migration have been accompanied by a declining rate of migration to Mexico City and to a lesser extent Guadalajara and Monterrey. Cities of intermediate size defined as 100000 to one million inhabitants have multiplied since 1970 and a few have achieved great economic and demographic dynamism. In 1970 16.6% of the population or 33.6% of the urban population lived in 37 intermediate cities while by 1990 nearly 23.7% of the population and 39.0% of the urban population lived in 56 intermediate sized cities. Census and survey data confirm the power of attraction of a group of intermediate cities but also reveal a complex array of situations. 24 of the 56 intermediate cities had populations of 100000-250000 and 21 had populations of 250000-500000. Most intermediate cities are located in the Northwest Center-North or Gulf regions. Some states have a number of intermediate cities and some have only one that concentrates most of the urban population. 26 of the 56 had growth rates over the two decades of over 4% annually and 20 had rates varying from 3% to 4%. 1990 census data show that 35% or more of the population were in-migrants in five cities: Tijuana Mexicali and Ensenada in the Northwest Cuernavaca in the Center-North and Cancun in the Yucatan peninsula. Between 20% and 34% of the population were in-migrants in 14 intermediate cities. Cancun and Tijuana had the highest proportions of recent migrants. The volume of net migration of most states generally reflected that of their intermediate cities. The economic crisis of the 1980s disproportionately affected the largest cities reducing their attractiveness.