Today through Sunday, volunteer doctors, dentists, nurses and other health workers will pile into Key Arena and start fixing people. It’s called the Seattle/King County Clinic. By the time it closes on Sunday, the volunteers will have served an estimated 4,000 patients, according a King County press release.

4,000 is a lot of people. Why don’t they have health insurance and a regular doctor already? Didn’t we already take care of that by expanding Medicaid under the Affordable Health Act, aka Obamacare?

King County is “one of the best Affordable Care Act success stories in the country,” in the words of executive Dow Constantine in a press release last week that announced that uninsurance rates have plummeted in King County since the implementation of the ACA starting in 2013. Then, 16.4 percent of adults were uninsured. As of last year, from when the most recent data is available, that’s fallen by more than half, to 7.7 percent. Yet given King County’s population, that means that more than a hundred thousand of our people still lack basic health insurance.Here’s a report from Seattle/King County Public health showing breakdowns by age, race and income. Insurance rates have climbed for each group over both of the past two years.

More people are in the system now. But not everyone. One of the biggest groups still mostly excluded from health insurance is undocumented immigrants. About 230,000 live in Washington.

The ACA has taken a licking in the news recently. Earlier this month, the Kaiser Family Foundation concluded that that monthly premiums (that is, membership dues) for some popular, cheaper individual health care insurance plans will increase next year. In August Aetna, a major health insurance company, announced it would withdraw from the ACA’s health care “marketplaces,” joining Humana and UnitedHealthcare. By requiring plans to cover riskier patients (i.e. the people who need health insurance the most), the ACA appears to have made to cost of doing business too high for those companies.

But recent Census Bureau data shows that while ACA premiums are rising faster than they had previously, they’re still 10 percent cheaper on average than employer plans. And then, of course, there’s the value of the law’s primary goal: between 2013 and 2015, the ACA reduced uninsurance rates in every congressional district in the country, according to FiveThirtyEight.

Washington has it better than a lot of states. In the 38 states that use the federal exchange on HealthCare.gov (as opposed to creating their own, like we did), the average second-lowest cost silver plans recently increased by 25 percent, according to a press release from the Washington Health Benefits Exchange. In Washington, on the other hand, those plans increase only 8 percent. “Nearly 70 percent of Washington Healthplanfinder customers who qualified combined to receive more than $28 million in tax credits in 2016, reducing premium costs by an average of $165 per month,” it says.

This post, including the title, has been edited.