The magic number is 2.08. This is the average number of persons per Seattle household in 2006, according to the American Community Survey. This is amazing and extreme! Our closest rivals among big cities are Portland and San Francisco at 2.24, and the national average is 2.61. Why is it so low?
A related statistic is the share of households that are families with children; the Seattle share is 19 percent, San Francisco 18 (lowest in the country), and Portland 24. (The U.S. average is 31 percent share of families with children.) Conversely, the share of non-family households (singles, unmarried partners) is 55 percent (33 for the U.S.). Seattle is only slightly behind the winner, San Francisco, in the share of adults never married (51 percent to 52 percent, 30 for the U.S.). Lastly, the proportion of the population under 15 is 13 percent in Seattle and San Francisco, 18 percent in Portland, and 20 percent nationally.
Those amazing demographic facts are only part of the story. Also remarkable is our share of adults with a college degree or higher, at 53 percent, the highest in the nation for a large city (U.S. is 27 percent), and we are tied with San Francisco for the highest share of professional and managerial workers, at 52 percent (U.S. average is 33 percent). And, fellow townsfolk, our share of SOV commuters is unusually low at 54 percent, compared to 76 percent nationally, and (ahem) a higher 61 percent for our rival new urbanist city, Portland. Over the period 1990-2006, according to the U.S. Census, median household incomes rose 100 percent in Seattle compared to 61 for the nation, and median family incomes 109 percent compared to 66 percent for the U.S. Finally, during that same 16 years, median housing values increased 3.3 times in Seattle compared to 2.3 times for the U.S.
These characteristics and changes are not a result of growth management, or the new urbanist vision underlying Seattle planning, or the mayor or City Council. Rather, the story is one of gentrification — that is, the partial replacement/displacement of the less affluent by more affluent (and professional and educated) households, as demonstrated by the data on income and home values. Planning has certainly encouraged this process, but already in 1990 the city had become a statistical outlier city by many of these measures. Planning reinforced market forces; but those singles, partners, professionals, and empty nesters recognized the inherent attractiveness of the city.
As to why Seattle is so unusual, I speculate that the number one reason is the presence of the University of Washington — its sheer size, its collosal research funding, its high-tech spinoffs. And to what do we owe its power? The key person was Sen. Warren Magnuson, who made possible the transformation of the UW into a great university through the development of the health sciences complex.
As for the rest of the greater Seattle metropolitan area (5/6 of it), it is by contrast to Seattle quite "normal" by national standards, which is why it absorbs over 90 percent of net job and population growth over the last 20 years. The city is what it is — neither good nor bad, a place characterized by a kind of intellectual class, created by self-selection and reinforced by idealist planning. Its outlier character makes Seattle a fabulous place for its advocates and probably the majority of its residents; but it is not the "right place" for the large majority of the metropolitan population and jobs. Fortunately the Seattle model depends on the character of its residents, noted above, and is not exportable to the rest of the urban region (however much Seattle idealists might believe).
The upside of the Seattle life is excitement, creativity, tolerance, and achieving a degree of "greenness"; the downside is housing and rent unaffordability, excess regulation/nanniness, and surprisingly, considering the rhetoric of urban village community building, a lack of sense of community, because of the high transiency of a non-family population. Sidewalk cafes may be symbolic, but PTAs and soccer leagues are real.