Is the Seattle area’s unprecedented population boom winding down?

Today we got another sign that it might be.

Population data released Thursday by the Census Bureau shows that, for the first time this decade, more people left King County than moved here from within the U.S.

It could be that the cost of living here is finally tipping the scales the other way.

From July 1, 2017, to July 1, 2018, the county had a net loss of about 5,000 people to other U.S. counties. The census data only includes the net population loss. It doesn’t give us the components behind that number — in other words, how many people moved into King County versus how many left.


Something else it doesn’t tell, unfortunately, is where all the folks who left went. But keep in mind that the net loss doesn’t necessarily mean that more people are leaving the Greater Seattle area. It could indicate that we’re losing more folks to Pierce and Snohomish counties, which are the two biggest recipients of King County expats every year.

Until 2018, King County has had a net gain from domestic movers every year this decade. The peak was in 2013, when nearly 12,000 more people arrived than left from other U.S. counties.

Last month, I reported on a slowdown in 2018 in the number of new driver’s licenses issued in King County to people moving in from out of state. So, this new census data doesn’t come as a complete surprise.

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But wait, there’s a twist.

Even as King County hit its lowest point this decade for domestic migration, international migration hit a new high.

The county had a net gain of about 21,500 people from other countries in 2018, up by about 4,000 from 2017. The gain in international migration was so great that it nearly made up for the loss in domestic migration. And yes, it also means that 100 percent of King County’s growth from migration last year was due to people moving here from outside the U.S.

The pattern of growth has completely flipped from the start of the decade. In 2011, the   county gained more new residents from other U.S. counties than it did from foreign immigration.


The  county attracts large numbers of workers from foreign countries — India and China, in particular — for the booming tech industry. Other fields, such as health care, also rely heavily on workers from outside the U.S.

In 2017, the  county’s immigrant population passed the half-million mark.

Migration is not the only driving force behind population growth. There’s also “natural increase” — that’s the number of babies born in the county, minus the number of people who died. In 2018, the county’s natural increase totaled roughly 12,500, which is just about average for this decade.

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Add up the natural increase and the international migration, and subtract the net loss from domestic movers, and you get a total 2018 population growth for King County of just under 29,000.

How does that stack up to previous years? It’s easily the smallest population increase so far this decade (Note: population estimates are typically revised after initial publication, and can go up a bit).

Even so, it’s an impressive number. Among all U.S. counties, King ranks sixth highest for numeric population growth last year. And King is the only county in the top 10 for numeric growth that’s not located in the southern half of the country. Maricopa County in Arizona, where Phoenix is located, ranks No. 1 with an 81,000-person increase.

Since 2010, King County has registered tremendous growth, adding about 300,000 people. As of 2018, the county’s total population stood at 2,223,000.

We may take population growth for granted around here but consider this: Since 2010, the majority of counties in the U.S. have experienced negative growth, according to the Census Bureau. About 53 percent — a total of 1,661 counties — have seen their population decline this decade.