How well health care reform is working depends a lot on which state you’re in, a newly released Gallup survey finds. According to the survey, the percentage of adults without health insurance is dropping fastest in states that have fully embraced the Affordable Care Act (ACA), aka Obamacare.

The uninsured rate among adults aged 18 and older in the states that have chosen to expand Medicaid and set up their own exchanges in the health insurance marketplace has declined significantly more this year than in the remaining states that have not done so. The uninsured rate, on average, declined 2.5 percentage points in the 21 states (plus the District of Columbia) that have implemented both of these measures, compared with a 0.8-point drop across the 29 states that have taken only one or neither of these actions.

Gallup reported that “states that have chosen to expand Medicaid and set up their own healthcare exchanges had a lower average uninsured rate to begin with: 16.1 percent compared with 18.7 percent for the remaining states – a difference of 2.6 points. The already notable gap between the two groups of states widened in the first quarter to 4.3 points.”