WASHINGTON — The turnout rate of black voters surpassed the rate for whites for the first time on record in 2012, as more black voters went to the polls than in 2008 and fewer whites did, according to a Census Bureau report released Wednesday.

The survey also found that Hispanics and Asians continue to turn out at much lower rates than other groups, and that women turn out at higher rates than men. The increase in black turnout was driven in significant part by more votes from black women.

According to the Census report, 66.2 percent of eligible blacks voted in the 2012 election, compared with 64.1 percent of eligible non-Hispanic whites. An estimated two million fewer white Americans voted in 2012 than in 2008, just as about 1.8 million more blacks went to the polls, more than 90 percent of them voting to re-elect President Obama, exit polls showed.

“In 2008, we changed the guard. In 2012, we guard the change,” said Michael Blake, who ran the Obama campaign’s effort to reach out to black and minority voters, Operation Vote.

The overall turnout rate nationwide was 61.8 percent in 2012, a decline from 63.6 percent four years earlier. Researchers cautioned that their estimates might overstate how many people voted across all categories, because they are based on surveys in which people were asked whether they had voted — a “socially desirable” activity.

Some researchers cautioned against treating 2012 as a watershed moment for the black vote. For example, Michael P. McDonald, an associate professor at George Mason University — using the same data but with a slightly different calculation — determined that black voters first turned out at a higher rate than whites in 2008.

Click here for the full story.