The portion of New Jersey and Pennsylvania residents without health insurance remained low in 2017, as insurance markets stabilized following sweeping changes by the federal Affordable Care Act to expand access to coverage.

About 5.5 percent of Pennsylvania residents were uninsured in 2017, as were 7.7 percent of New Jersey residents, according to new data from the U.S. Census Bureau's American Community Survey released Wednesday. Uninsured rates decreased by one-tenth of a percent in Pennsylvania and two-tenths of a percent in New Jersey between 2017 and 2016.

The national uninsured rate was unchanged in 2017, compared with the previous year, at 8.7 percent.

"It reflects a few offsetting trends," Katherine Hempstead, a senior policy adviser with the Robert Wood Johnson Foundation, said of the low, stable uninsured rates.

Premium increases in the individual market, including the health insurance exchanges established by the ACA, may have proven too steep for some people, who went without coverage in 2017.

At the same time, steep competition for workers amid a strong labor market has pushed some companies to expand their health insurance offerings, including coverage for part-time employees, who typically do not qualify for such benefits, Hempstead said.

Medicaid expansion has also had a significant effect on uninsured rates.

Between 2013, the year before states began expanding Medicaid eligibility, and 2017, the uninsured rate declined 4.2 percent in Pennsylvania and 5.5 percent in New Jersey.

"This size change is something that's really associated with states that expanded Medicaid. You see a real closing in income disparities in insurance coverage," Hempstead said.

Nationally, about 19 percent of people were covered by Medicaid in 2017.

Private insurance, either from an employer or bought independently, was the most common kind of insurance, covering 67 percent of Americans.

It's unclear whether the trend will continue in the years ahead.

Republican efforts to dismantle the Affordable Care Act, such as eliminating the penalty for people who do not buy health insurance and expanding access to lower-quality health plans, as well as work requirement rules for Medicaid could lead to more people going without health insurance.

At the same time, premium rates stabilized in many states in 2018 and insurers spooked by the ACA are returning to the marketplace. In New Jersey individual insurance rates for 2019 will decline by an average of 9.3 percent.

New Jersey, in particular, has taken several steps to protect its insurance marketplace from potential national disruptors.

It is one of only three states and the District of Columbia to establish its own individual mandate, requiring most residents to buy health insurance or pay a tax penalty. The state attributed its uncommon decline in insurance premiums to its new reinsurance program, which will reimburse 60 percent of individual claims between $40,000 and $215,000.

"The next sort of big challenge for us is to see if, as a nation, we can go lower," Hempstead said.

Many of the people who remain uninsured are eligible for Medicaid, subsidies in the Obamacare marketplaces, or are passing up employer-sponsored health benefits, she said.

"Pretty much everyone who isn't covered, the reason is, on some level, that they don't think they can pay for it. The biggest barrier for coverage remains the cost of health care."