More good news from the Affordable Care Act: Since it became the law of the land, uninsurance disparities between white, black and Hispanic residents have narrowed significantly.

In a study published this month in the journal Health Affairs, researchers found that by the fourth quarter of 2014, the uninsurance rate for Hispanic adults had fallen to 31.8 percent from about 40 percent in the third quarter of 2013. During the same time period, uninsurance among black adults declined from 25.5 percent to 17.2 percent, while uninsurance among white adults fell from 14.8 percent to 10.5 percent. Those gains resulted in reductions in the absolute disparity rates in uninsurance for black and Hispanic adults living in states that expanded Medicaid eligibility and in states that didn’t expand Medicaid. (According to the study: Absolute disparity is the difference between the percentage uninsured for blacks or Hispanics and the percentage uninsured for whites. Relative disparity is the ratio of the percentage uninsured for blacks or Hispanics to the percentage uninsured for whites.) The study is based on data from the 2014 National Health Interview Survey.

Specifically, researchers found that for Hispanics, the absolute disparity narrowed by 4.2 percentage points. Among black adults, the absolute disparity in uninsurance fell from 7.4 percentage points in 2013 to 4.1 percentage points in 2014. In states that did not expand Medicaid eligibility, the absolute disparity for black adults dropped from 11.1 percentage points to 4.8 percentage points. Among Hispanic adults, the absolute disparity went down in states that expanded Medicaid and in those that didn’t. However, in a surprise to the researchers, relative disparities in uninsurance increased for Hispanics living in states that expanded Medicaid — in those states, Hispanics were more than three times more likely to be uninsured than whites in 2014, compared to 2.7 times as likely in 2013. Also, whites experienced no significant declines in uninsurance in states without a Medicaid expansion.

Overall, all groups experienced a decline in uninsurance, which translated into narrowing absolute disparities among blacks and Hispanics in both expansion and nonexpansion states. (A little background for those unfamiliar with the Medicaid expansion: The ACA authorized and provided funding for Medicaid eligibility expansion in every state. Unfortunately, a 2012 Supreme Court ruling made Medicaid expansion optional and so as of September 2015, only 31 states and Washington, D.C., had expanded their Medicaid programs.)

Study authors Stacey McMorrow, Sharon Long, Genevieve Kenney and Nathaniel Anderson write:

Substantial additional progress on reducing disparities in uninsurance under the ACA will require expanding Medicaid in all states. For example, one recent study projected that with all states expanding Medicaid eligibility, the absolute black-white disparity in the uninsurance rate would be reduced to 2.6 percentage points. Targeted education, outreach and enrollment efforts related to Medicaid and the Marketplaces may also be particularly important for members of racial and ethnic minority groups, who have been shown to have more limited health insurance literacy than their white counterparts.

The researchers hypothesized that the coverage gains among blacks in nonexpansion states may be due to robust Health Insurance Marketplace enrollment activities and increased Medicaid participation among those who were already eligible for the insurance program before expansion. They also cautioned that “significant gaps” remained in uninsurance rates for blacks and Hispanics when compared to whites. Among Hispanics, the authors wrote that persistent disparities in coverage are likely a result of restricting immigrant access to Medicaid and federal subsidies within the insurance exchange, making it “important to monitor disparities for the undocumented immigrant population as ACA implementation continues.”

To request a full copy of the study, visit Health Affairs.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.