PubMed1974
The population changes in San Jose and St. Louis between 1960 and 1970 exemplify the two broad trends-urban formation followed by metropolitan dispersal-that have shaped 20th-century urbanization in this country. The fact that these developmental trends were expressed through demographic processes found to be common to both cities, despite their contrasting recent experiences, suggests that generalizations can be made about the complex forces underlying urbanization. The formation of metropolitan San Jose's population parallels the traditional process whereby a region's growth comes to be focused, through migration, on a few urban centers. The modern variant is not characterized by a rural-to-urban shift, however, but by migration flows among urban areas, and particularly to a few most-favored areas, such as San Jose. Migratory growth has left a powerful demographic legacy in San Jose. This legacy is also instructive for studying the migratory formation of any new city's population. Its demographic character determines its demographic destiny, whose likely variations we can now perceive with some clarity. San Jose's population is both youthful and chronically migratory. The presence of many prospective parents and relatively few elderly persons lays a broad foundation for the population's continued growth through natural increase, despite the national downturn in fertility (14). Even without further net in-migration, the population of new cities like San Jose would continue to grow at an above-average rate. The hypermobility of San Jose's population (that is, its propensity for further migration) also has an important bearing on the future. With about 21 migrants entering and 17 departing each year per hundred residents, San Jose's rapid migratory growth rests (as it would in other new cities) on a precarious arithmetic balance. A significant dip in local employment growth could easily reduce net migration to a small fraction of its present high level. Even a slight decline would result in the inflow's no longer exceeding the high volume of outflow. Demographic analysis alone cannot foresee such an employment downturn, but if it happened, the migratory downturn probably would be swift. Hypermobility also works the other way; and given San Jose's focal position in California's expanding metropolitan structure (with its virtually endless supply of migratory growth), net migration could resume with equal swiftness. The outward dispersal of population from central cities that has occurred in St. Louis has been accelerating in other cities as well, and will remain a prominent feature of U.S. urban growth. It may seem paradoxical that in a period noted for something called "urban growth" there are so many declining central cities, but that is merely one indication that the "central city" no longer is the real city, except in name. Real city or not, the central city can expect to come into political conflict with other jurisdictions created in the process of dispersion. In cities like St. Louis, where population is dispersing but old political boundaries are fixed, the problems of the central city are separated from the resources in the suburbs. Transitional problems associated with persistent and severe outmigration also arise: accumulation of disadvantaged citizens, declining demand for city housing, and a diminished replacement capacity in the population. Carried far enough, the last of these problems results in natural decrease, and thereafter the population's decline acquires its own dynamic. As noted earlier, the white population in St. Louis has reached this point: The number of persons dying now exceeds the number being born. For two reasons, this natural decrease can do little other than intensify. First, a substantial proportion of whites are either entering or already within the high-mortality age brackets. The white population's crude death rate therefore will continue to rise. Second, prospective parents are becoming scarce among St. Louis's whites, and the national evidence that parents in general will choose to have smaller families continues to mount. The white population's crude birth rate is therefore likely to fall, barring a dramatic increase in fertility or a strong and sustained inflow of childbearing families. Nor is St. Louis's black population likely to grow substantially. It is expanding steadily through natural increase, but black migration out of the city is more than enough to cancel that increase.