King County lost population last year for the first time in almost 50 years

I wasn’t in the Seattle area in the early 1970s, during the infamous “Boeing Bust.” But those who were remember it as a grim time. The aerospace giant, the largest employer in the region at the time, teetered on bankruptcy and laid off more than half its workforce.

Seattle was so down and out that a couple real estate agents put up a billboard in SeaTac reading, “Will the last person leaving Seattle — turn out the lights.”

The reason I bring up this painful chapter in local history?

That’s how far back I had to go in U.S. Census archives to find the last time that King County had a one-year drop in population — from 1971 to 1972, the county lost about 11,000 residents.

New census data shows that last year, it happened again.

Between July 1, 2020, and July 1, 2021, King County’s population dropped by around 20,000, or 0.9%. The population estimate for 2021 is about 2.25 million.

Not a huge decline, to be sure — but it’s still notable when you consider the county’s 49-year run of population growth. And in recent years, King County didn’t just grow modestly — it was among the fastest-growing large U.S. counties, gaining 320,000 people from 2010 to 2019.

In the last one-year period before the pandemic changed everything, from July 1, 2018, to July 1, 2019, King County had a net population growth of about 24,400.

Needless to say, the pandemic is to blame for the decline last year, at least in part. Let’s take a look at the components of change to see what happened.

There are two ways that population can grow: migration (domestic and international) and “natural increase,” which is births minus deaths.

The pandemic, of course, greatly curtailed the movement of people between countries, which had a dramatic effect on international immigration. This hit King County particularly hard because international migration was the primary driver of growth in the previous decade.

In the 2018 to 2019 period, the county gained about 18,000 people through international migration. Last year, that number fell to just under 6,000. It’s still an increase, but paltry compared with the previous decade.

Domestic migration — that is, people moving here from other counties in the U.S. — fell even more. In fact, domestic migration had already started to trail off by end of the previous decade. In the 2018-19 period, the number of people who left King County exceeded the number who moved here from within the U.S. by close to 5,000.

But last year, the population loss to other counties was dramatically larger. King County had a net loss of nearly 33,000 people from domestic migration. If you want to know the primary reason our population declined, look no further.

It seems likely that the pandemic played a role here, too. The rise of remote work made it possible for many people who work in the county to live elsewhere. The ever-rising cost of housing in King County couldn’t have helped matters either.

The Census Bureau only provides a net figure for 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. We also don’t know from this data how much of the county’s population loss came from the city of Seattle versus the surrounding areas.

Another thing the data doesn’t tell us, unfortunately, is where all the folks who left King County went. But typically, Pierce and Snohomish counties are the two biggest net gainers from King. (Incidentally, both Pierce and Snohomish counties had modest population gains from 2020 to 2021.)

Finally, there is natural increase, and compared with a “normal” year, deaths were higher and births were lower. There was still a net increase, but it was only a gain of less than 7,000. In the 2018 to 2019 period, the natural increase was about 12,500.

The higher number of deaths (there were around 16,500) is surely due, at least in part, to COVID-19. Even the lower number of births (about 23,000) could be related to the pandemic — nationally, there was a “baby bust,” which public health officials have linked to the pandemic.

Add up all these components of change and get the 20,000-person deficit.

King was one of many large U.S. counties to shrink last year. Among the 15 most-populous counties, 10 had a net loss of residents. Kings County, New York — better known as Brooklyn — shrank by more than 3%, the largest decline among the top 15 counties.

Many of the areas that experienced strong growth are in the Sunbelt. Maricopa County, Arizona, where Phoenix is located, had the largest numeric population increase of any county, at about 58,000.

The million-dollar question is whether this population decline represents a pandemic-era blip — or is it the start of trend? For that answer, we’ll simply have to wait and see.