The Seattle area continues to be among the nation’s strongest magnets for young adults. The Indexer documented the phenomenon of certain metro areas attracting far more than their share of migrants in their 20s and 30s. With the release of the latest 2019 data from the American Community Survey, we see Seattle and Denver tied for first place among the largest metro areas in the share of their populations held by Millennials.
Figure 1 shows the percentage of population of the 25 largest metro areas in the country that is between the ages of 25 and 40. This bracket, with people born between 1979 and 1994, closely matches the generally accepted range of the large Millennial generation.
Seattle comes in just behind Denver, although their positions are statistically indistinguishable. If we expand the list to the top 50 metro areas, Austin comes in just ahead of Denver and Seattle. Seattle passed San Francisco sometime in the past few years.
The past few years has also seen the Millennial cohort move firmly into the age range of family formation. So, are all these younger adults in Seattle having children? If so, we would see the Seattle metro area also leading the pack in the number of children. Figure 2 shows children under the age of 10 as a share of the population for the same 25 largest metro areas.
Here we see Seattle drop back to the middle of the group, although not falling as far as the other leading Millennial cities of Denver, San Francisco and Portland. This raises the question of whether there is a relationship between the number of adults of typical child-bearing age, and the actual number of children. Figure 3 shows the share of the population under the age of 10 against the share between 30 and 40 (most likely to be the parents of the under-10 kids), for the 50 largest metro areas.
There is really no relationship at all. The correlation of .083 is quite weak, and factoring in the error margins on the data, we cannot say with any certainty that having more young adults will yield more children in a metro area. The green dot represents the country as a whole, where there are 10 children under 10 for every 11.3 adults age 30 to 40. In Seattle, the red dot, there are 10 children under 10 for every 14 adults age 30 to 40.
So, why are the young adults who flock to the thriving coastal metro areas not having children there at a higher rate? We know that, from a nominal income perspective, they can afford it—Seattle has among the highest incomes in the country.
The answer may lie in a demographic phenomenon that is difficult, if not impossible, to track: the boomerang effect. We know from migration data provided by the IRS that there is a huge churn of population that is often masked by the focus on “net” migration. In 2018, the most recent year for which we have data, Washington gained a net of about 30,000 people, but that was the result of 214,000 people moving into the state and 184,000 people moving out. A good share of those moving out were likely young adults who had moved to Seattle in the past decade. They had “done their time” in Seattle and were heading back to the place where they grew up—almost certainly more affordable than Seattle—in order to start a family.
The finding that the Seattle areas has fewer children than its population of young adults would indicate is consistent with the Indexer’s other finding about the growth in the proportion of households living in multi-family housing. Americans, especially on the West Coast, very rarely choose to raise children in attached housing. So it is quite possible that young people who want to start families are leaving the Seattle area in substantial numbers. But the implications are not really clear. Do we have a normal underlying, stable demographic with this churning of young adults layered on top? Or do we face real imbalances that will play out over time? We will know a whole lot more when the 2020 census data comes in and we get fine grained measures of age at the census tract level.
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