The latest US Census Bureau migration data shows that people continue to move from principal cities (which include core cities) in metropolitan areas to what the Census Bureau characterizes as "suburbs" (Note). Between 2011 and 2012, a net 1.5 million people moved from principal cities to suburbs (principal cities lost 1.5 million people to the suburbs). The movement to the suburbs was pervasive. In each of the age categories, there was a net migration from the principal cities to the suburbs. There was also net migration to the "suburbs" in all categories of educational attainment.
These data are in contrast to claims that people are moving from a suburbs to central cities. Virtually none of the migration data has shown any such movement. Moreover, the city population estimates produced for 2011 by the Census Bureau, which indicated stronger central city growth have been shown to be simply allocations of growth within counties, rather than genuine estimates of population increase.
Note on Census Bureau "Suburbs:"
The movement to the suburbs is undoubtedly understated in the Census Bureau estimates, because many jurisdictions included in the "principal city" classification are in fact suburbs. The Real State of Metropolitan America showed that virtually all population growth in principal cities was either in suburban jurisdictions classified as principal cities, or in cities with substantial expenses of post-World War II automobile oriented (or suburban) land-use patterns. The remaining core cities that are largely only urban core in land use accounted for only 2% of principal city growth from 2000 to 2008.
For a decade, the Census Bureau has used a "principal city" designation instead of the former "central city" term. All former "central cities" are "principal cities." The Census Bureau characterizes all other areas of metropolitan areas as "suburbs." In fact, many of the principal cities are functionally suburbs, having barely existed or not existed at all at the beginning of the great automobile oriented suburban exodus following World War II.
Examples of such suburban principal cities, with their metropolitan areas in parentheses, are Hoffman Estates (Chicago), Arlington (Dallas-Fort Worth), Aurora (Denver), Fountain Valley (Los Angeles), Eden Prairie (Minneapolis-St. Paul), Mesa (Phoenix), Hillsboro (Portland), San Marcos (San Diego), Pleasanton (San Francisco), Kent (Seattle), Virginia Beach (Virginia Beach-Norfolk) and many others.