IRS Data Shows Most of King County’s Population Loss Is Staying Within Washington
Joy Ale
July 21, 2026
IRS Data Shows Most of King County's Population Loss Is Staying Within Washington
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New Internal Revenue Service migration data shows King County experienced a net domestic population loss between the 2022 and 2023 tax years, though the majority of residents who left did not move far. Based on changes in tax return addresses, about 105,000 people moved out of the county while roughly 92,000 moved in, resulting in a net loss of approximately 13,000 residents. The migration also had an economic impact, with departing residents taking an estimated $8.7 billion in adjusted gross income (AGI), compared with $6.7 billion brought in by newcomers.
The data suggests the county’s population decline is being driven primarily by relocation to other parts of Washington rather than an exodus to lower-tax states. Nearly 48,000 residents moved to other Washington counties, while about 30,000 moved into King County from elsewhere in the state. Neighboring Pierce and Snohomish counties recorded the largest net gains, followed by Kitsap and Thurston counties, reinforcing concerns that Washhousing affordability and rising living costs are pushing residents to nearby communities.
Despite those in-state losses, King County continued to attract people from across the country. The county gained nearly 5,000 more residents from other states than it lost, with the largest influxes coming from Los Angeles County, Honolulu County and California’s Alameda County. However, the county also recorded notable out-of-state losses to Arizona’s Maricopa County, Manhattan in New York and Williamson County in the Austin, Texas, metro area.
While King County posted a net population gain from interstate migration, the financial picture was less favorable. IRS figures show the county experienced a net loss of roughly $446 million in adjusted gross income to out-of-state migration, indicating that those leaving Washington generally had higher incomes than those moving in. The findings highlight the growing challenges surrounding housing affordability, workforce retention and the county’s long-term economic outlook.
