Today marks the one-year anniversary of several elements of the Patient Protection and Affordable Care Act, notably the provision allowing young adults up to age 26 to stay on or join their parents’ employer-sponsored health insurance policy.

Several folks blogged about this last week, notably Health and Human Services Secretary Kathleen Sebelius, Sara Collins, Tracy Garber, and Karen Davis of the Commonwealth Fund, and writer Jonathan Cohn. They all cited the newly released Census data on health insurance, which detailed how  the uninsured rate for young adults, 18-24, fell between 2009 and 2010 and, in fact, this was the only age group with a statistically significant decline in their uninsurance rate. They argued that the health insurance provision allowing young adults to stay on or join their parents’ employer-sponsored health insurance policy is to credit for this up-tick in coverage.

This week, Kevin Sack of the New York Times, wrote a piece reiterating their points, with more recent data through March 2011 from the National Health Interview Survey. While there’s much hand-waving about how we can credit health reform for the increase in health insurance coverage among young adults, it’s relatively easy to compare health insurance numbers with labor market statistics to find compelling evidence of initial signs of health reform success.

In this figure, I compare changes in the employment rates and the rate of employer-sponsored health insurance for various age groups between 2008 and 2009. As you can see, employment rates fell for each group as did employer-sponsored health insurance.  This is not surprising given the fact that most people find health insurance on their own job.

Click figures to enlarge

Next, I compare these same changes in employment rates and health insurance rates for various age groups between 2009 and 2010. As you can see, the job-market didn’t do young adults any favors. In fact, their employment rate actually fell further than any other age group. Given the close relationship between labor market outcomes and employer-sponsored insurance, we would expect declines in coverage for all groups.  What we see instead is that employer-sponsored health insurance actually rose among young adults, while it fell for all other groups.

So, how many young adults took advantage of this new provision? A back of the envelope estimate of what young adult coverage rates would have been if the 2008-09 relationship between employment and insurance had held for 2009-10 would be a 1.1 percentage point drop in insurance rates for young adults in 2010. Instead, we see here that insurance rates actually rose by 0.6 percentage points instead of falling by 1.1 percentage points — basically, this means that up to 490,000 young adults may have obtained coverage in 2010 because of the health reform provision.

Given the fact that the labor market continued to decline for young adults, my guess is that a closer look at the Census micro-data would confirm the fact that a greater number of young adults are gaining dependent coverage through their parents’ policies.  Even without that added analysis, these figures alone are compelling evidence in support of the argument that health reform is beginning to work.