The percentage of Americans without health insurance did not decline on 2017, marking the first time since the passage of the Affordable Care Act that the uninsured rate held steady.

According to the Census Bureau,

The Census report also confirmed the growing chasm between states that decided to take advantage of the ACA's Medicaid expansion and those that did not.

The ACA, better known as Obamacare, allowed states to expand Medicaid coverage to people making up to 138% of the federal poverty line. Since then, 31 states and Washington, DC, have adopted the expansion.

"In states that expanded Medicaid eligibility ('expansion states'), the uninsured rate in 2017 was 6.5%, compared with 12.2% in states that did not expand Medicaid eligibility ('non-expansion states')," the Census Bureau said in the report.

In fact, the uninsured rate in states that did not expand Medicaid went up 0.7 percentage points compared to the stable rate in states that did expand Medicaid. Since 2013, the uninsured rate in expansion states is down 7 percentage points, compared to just 5.3 percentage points in non-expansion states.

Matt Broaddus, a senior research analyst at the left-leaning Center of Budget and Policy Priorities, pointed to the studies that showed a large swath of the uninsured are eligible for cheap coverage under the ACA as evidence that the uncertainty and lack of outreach were the cause of the stall.

"Kaiser Family FoundationUrban Institute

nior vice president at the Kaiser Family Foundation, a nonpartisan healthcare think tank, said the new data is inconclusive to make a determination either way.