New U.S. Census numbers released Wednesday found that the number of uninsured residents in Connecticut dropped from 397,000 in 2010 to 303,000 in 2011.

That means about 8.6 percent of Connecticut residents were uninsured last year. The decrease in the number of uninsured can be attributed largely to the Affordable Care Act, which allowed 23,000 young adults in Connecticut under the age of 26 to remain on their parents insurance.

Connecticut was ahead of the curve in allowing young adults to stay on their parents insurance until the age of 26. The General Assembly passed legislation back in 2007. It went into effect on Jan. 1. 2008, so the 2011 increase may not be statistically significant.

According to the latest Census numbers, employer-sponsored coverage accounted for 24,000 of the increase for those covered by insurance in 2011, but the majority was due to increases in Medicaid and Medicare enrollment.

The “numbers confirm that health care reform measures enacted by both state and federal policy makers are working and that efforts in our state in the past few years helped the social safety net hold firm during our recent recession,” Frances G. Padilla, president of Universal Health Care Foundation of Connecticut, said. “We need to continue to monitor the process of implementing federal and state health reform to ensure that the cost control measures and coverage provisions, such as the 2014 launch of the Exchange marketplace, serve individuals and small businesses by offering quality, affordable insurance products.”

An analysis of the numbers by Connecticut Voices for Children concluded there were “no statistically significant changes in Connecticut uninsured between the most recent two-year period (2010-2011) and the previous period (2008-2009).”

The advocacy group argued that because of the small sample survey sizes two-year estimates should be used to evaluate trends.

Looking back over the years, the advocacy group found the number of uninsured over the past decade has increased based on comparing the two-year averages.

“There was a statistically significant increase over the last decade in the percentage of all Connecticut residents who lacked health insurance during the entire previous 12 month period, rising from 8.6 percent in 2000-2001 to 9.9 percent in 2010-2011. There was no statistically significant change over the decade for uninsured children,” it concluded in its analysis.

Secondly, “There was a statistically significant decline in the percentage of people under age 65 in Connecticut who had employment-based health coverage over the decade, dropping from 78 percent in 2000-2001 to 69.8 percent in 2010-2011.”

“There was a similar significant decrease in children who were covered by employment-based insurance – from 77.8 percent in 2000-2001 to 67.4 percent in 2010-2011,” it found.