Attention Obamacare haters: The law you despise appears to be working.

The Census Bureau this morning released its annual report on income, poverty, and health insurance. My colleagues will be back later to discuss the income findings, but I want to flag the health care numbers right away. For the first time in three years, the proportion of Americans who have health insurance went up, from 83.7 percent in 2010 to 84.3 percent in 2011.

And what explains the shift? The breakdown by age offers some clues. Relative to last year, the percentage of young adults with health insurance rose by 2.2 points. That was the largest increase of any group. And it was the second year in a row that coverage among young adults increased. Overall, according to Census officials, the percentage of young Americans has gone up by about 4 percent during that span.

As you probably know, the Affordable Care Act allows young adults to enroll on their parents’ health insurance plans if they have no access to coverage on their own. That provision surely doesn’t account for all of the young adults getting coverage. But it surely explains a lot of it.

Larry Levitt, a leading expert on health care policy and senior vice president at the Kaiser Family Foundation, offered this assessment via e-mail: