The number of Americans without health insurance is creeping back up, after seeing a big drop once the Affordable Care Act took effect, according to the latest tracking survey from the Commonwealth Fund.

The numbers that matter: About 15.5% of adults are uninsured, by Commonwealth’s count, up roughly three percentage points from the same time in 2016. That represents an increase of about 4 million people, the organization said.

Between the lines: Lower-income families saw the biggest coverage losses. Families making more than about $60,000 per year saw relatively stable coverage levels.

The context: Commonwealth attributes the increase largely to the way Congress and the Trump administration has handled the ACA.

• The survey accounts for all sources of coverage, not just the individual market or the ACA’s exchanges, but lower-income households are more likely to rely on the exchanges or the ACA’s Medicaid expansion.

Yes, but: Roughly 11.8 million people selected insurance plans through the ACA’s exchanges in the most recent open enrollment period — nearly identical to the number who bought coverage for 2016.