Cities have been pivotal role to improved living standards, because of the opportunities they facilitate. This is particularly evident over the past two centuries, as world urbanization has risen from 3 percent to over 50 percent, and to more than 80 percent in the United States.
Many American cities, described commonly as urban cores, are functionally more suburban and exurban, based on urban form, density, and travel behavior characteristics. Data from the 2010 census shows that 42.3 percent of the population of the historical core municipalities was functionally urban core (Figure 1). By comparison, 56.3 of the population lived in functional suburbs and another 1.3 percent in functionally exurban areas (generally outside the urban areas). Urban cores are defined as areas that have high population densities (7,500 or per square mile or 2,900 per square kilometer or more) and high transit, walking and cycling work trip market shares (20 percent or more). Urban cores also include non-exurban sectors with median house construction dates of 1945 or before. All of these areas are defined at the zip code tabulation area (ZCTA) level, rather than by municipal jurisdiction. This is described in further detail in the “City Sector Model” note below.
The very centers of urban cores in many major metropolitan areas are experiencing a resurgence of residential development, including new construction in volumes not seen for decades. There is a general impression, put forward by retro–urbanists and various press outlets that the urban core resurgence reflects a change in the living preferences of younger people – today’s Millennials – who they claim are rejecting the suburban and exurban residential choices of their parents and grandparents.
Much attention has been given the increase in transit use in America. In context, the gains have been small, and very concentrated (see: No Fundamental Shift to Transit, Not Even a Shift). Much of the gain has been in the urban cores, which house only 14 percent of metropolitan area population. Virtually all of the urban core gain (99 percent) has been in the six metropolitan areas withtransit legacy cities (New York, Chicago, Philadelphia, San Francisco, Boston, and Washington).
Philadelphia was America’s first large city and served as the nation’s capital for all but nine months between the inauguration of George Washington is the first president in 1789 and the capital transferred to Washington, DC in 1800. Before the early 1900s, the United States Census Bureau had not developed a metropolitan area (labor market area) concept. However, the website peakbagger.com has attempted to define earlier metropolitan areas based on concepts similar to those used today. In the case of Philadelphia, this is important, because it was somewhat unique in having virtually adjacent, highly populated suburbs that make comparisons of municipal populations (the only population data available) misleading.
There is an increasing recognition – at least outside the academy, planning organization and urban core developer groups – that the spatial expansion of cities or suburbanization represents the evolving urban form of not only the United States and virtually all of the high income world but also across the developing world, whether middle income or third world.
In recent years, Mexico has made substantial economic progress. Per capita income (purchasing power parity) in Mexico exceeds that of all the “BRIC” nations (Brazil, Russia, India, and China) except resource-rich Russia.
The 2013 annual metropolitan area population estimates by the US Census Bureau indicate a continuing and persistent dominance of population growth and domestic migration by the South. Between 2010 and 2013, 51 percent of the population increase in the 52 major metropolitan areas (over 1 million population) was in the South. The West accounted for 30 percent of the increase, followed by the Northeast at 11 percent and eight percent in the North Central (Midwest).