The Seattle Times recently ran an article on population change in cities, with the headline “Seattle drops out of top 5 for growth among major U.S. cities.” The article, about growth within the Seattle city limits between 2018 and 2019, was unusual in its focus on the growth of individual cities in a national context. National population growth comparisons generally focus on metropolitan areas. On that basis, the Seattle metro area ranked 29th out of the largest 100 metro areas for growth between 2018 and 2019. Not exactly blistering.
The growth patterns of large urban areas are nearly always rooted in economic change (natural disasters being an exception). Metro areas are the basic unit of urban economic geography, defining markets for labor, real estate and regional services. Cities are political entities, the boundaries of which almost never align with market forces. Large metro areas have dozens of cities carving up the economic activity that the area supports. As we will see below, the relative shares of growth taken by central cities and their surrounding areas varies quite a bit.
The growth of metro areas is one interesting question, and the relative growth of cities within a metro area is another interesting question. But comparing individual cities by themselves across the country does not tell us much. The article notes that the fastest growing large city is Mesa, Arizona. But Mesa is part of metropolitan Phoenix, so Mesa’s growth is part of the story of the growth of the entire Phoenix area.
The city of Seattle itself has, indeed, grown very fast in the past decade, due to the influx of young people occupying the rapidly proliferating high-rise and mid-rise neighborhoods of the city. That tells us interesting things about how growth is distributed in the region, but not too much about why the region itself is growing. The technology firms that are driving regional growth look first at the overall labor market of the Seattle area, and then decide where within the area to locate. Seattle has been capturing a large share of that growth, but the regional labor market is pulling it in. The region’s success in technology-driven income growth has, however, not been matched by population growth: high housing costs and dicey weather keep the region out of the growth leagues of the Sunbelt.
The position of central cities within their metro areas varies widely. Figure 1 shows the population of the 25 largest metro areas in the country, the population of the central city of each metro area, and the share of metro population that the central city contains.
The variation in that share is large. San Antonio contains 61 percent of the population if its metro area, and San Diego and New York contain 43 percent of their region’s populations. In contrast, Miami and Atlanta contain only 8 percent of the population of their massive metro areas. Seattle has about 19 percent of the metro area population, which is slightly below the big city average.
The wide variation in the last column of Figure 1 comes from different paths of metro area growth. Once Seattle settled its boundaries in the 1950s, the areas to the north and south declined to annex to it. Shoreline became its own city in 1995 and the areas to the south of Seattle remain unincorporated. There are now 75 separate cities in the Seattle metro area. Phoenix, in contrast, annexed many surrounding areas as they developed in recent years, and now has 34 percent of its much larger regional population, with the rest spread out among just 26 other cities, including Mesa.
Figure 2 shows growth rates for metro areas, central cities and the balance of the metro areas outside of the central cities, for the 25 largest metro areas, ranked by total growth.
Among these metro areas, Seattle had the fastest growth for a central city from 2010 to 2020. But at the same time, the balance of the Seattle metro area ranked only ninth for growth. This is the opposite pattern of Houston, which ranked first for growth outside the central city, while Houston itself was ranked 14th among central cities.
Considerable ongoing work within the field of urban economics focuses on the question of how people and firms decide where to locate within a metro area. Theories of spatial equilibrium and the field of public choice both focus on the tradeoffs that people and firms make between land costs, transportation, taxes, services and amenities.
In the post-COVID world, the distribution of growth among and within metro areas will change, as safety become a new and large decision factor. At the national level, we are already seeing strong growth in mid-sized metro areas, and concerns about contagion may draw people to less crowded, less globally connected places. Among the 100 largest metro areas, Boise was the second fastest growing last year, while Provo was fourth fastest and Spokane was 12th fastest growing.
At the local level, safety will also figure into decisions about where in a metro area people might want to live. Dense cities may seem less appealing if they bring added health risks from proximity and face restrictions on all the exciting amenities that make city living attractive. And if the shift to telecommuting becomes more permanent, we could see rapid growth in communities just outside the Seattle metro area, which feel safer and are still close enough for an occasional visit to the office.
New tradeoffs and preferences could give rise to some very different metropolitan growth patterns in the decade ahead.