Health coverage gains under the Affordable Care Act were concentrated where they were needed most—among lower-income groups and in the five boroughs of New York City—recently released Census Bureau data show.

Between 2013 (before Obamacare took full effect) and 2016, the number of uninsured New Yorkers below age 65 declined by 884,211, according to Small Area Health Insurance Estimates released on March 28.

Just over half of that drop occurred in New York City, and 56 percent involved people living at or below 200 percent of the federal poverty level, or $50,200 for a family of four.

This was to be expected, because low-income groups and New York City have had higher uninsured rates than the state as a whole.

The state’s overall uninsured rate dropped by five points, from 12.4 percent in 2013 to 7.1 percent in 2016.

In New York City, the rate dropped six points, from 15.1 percent to 8.9 percent. And among people below 200 percent of poverty, the rate dropped eight points, from 19.5 percent to 11.1 percent.

The county with the highest uninsured rate in both 2013 and 2016 was Queens, at 19.2 percent and 11.3 percent, respectively. Yet that eight-point drop—corresponding to 153,000 more people with insurance—was also the largest of any county.

The county with the lowest uninsured rate in both years was Saratoga, at 7.3 percent and 4.3 percent respectively.

The Census Bureau makes its estimates based on surveys, and they appear to understate coverage gains among low-income populations.

The bureau’s data shows that the uninsured population eligible for Medicaid dropped by 342,000. That’s less than half the state’s Medicaid enrollment gain of 769,000 from 2013 to 2016, as reported by the U.S. Centers for Medicare & Medicaid Services.