The decline may be due to the down economy: Other research suggests people are still drinking as heavily as in years past, so some may just be finding cheaper ways of imbibing than by going to bars, night clubs and restaurants.
"One possibility is that people are drinking at home more and driving less after drinking," said Dr. Thomas Frieden, director of the Centers for Disease Control and Prevention.
The CDC statistics — released Tuesday — are based on a 2010 national telephone survey of about 210,000 U.S. adults. The respondents were kept anonymous.
Nearly 1 in 50 said they'd driven drunk at least once in the previous month. That equates to about 4 million Americans driving drunk last year.
About 60 percent said they drove drunk just once, but some said they did it daily.
That led to a CDC estimate of more than 112 million episodes of drunk driving in 2010. That's more than 300,000 incidents a day.
CDC officials lamented that finding; still, it was the lowest estimate since the survey question was first asked in 1993, and down significantly from the 161 million incidents in the peak year of 2006.
Young men ages 21 to 34 were the biggest problem, accounting for just 11 percent of the U.S. population but 32 percent of the drunken driving incidents.
The overwhelming majority of drunk driving incidents involve people who had at least four or five drinks in a short period of time. But binge drinking has not been on the decline, other health research suggests.
The National Highway Traffic Safety Administration has also noted signs of an apparent recent decline in drunk driving. According to that agency's latest data, the number of people killed in U.S. crashes involving alcohol-impaired drivers dropped from 11,711 in 2008 to 10,839 in 2009.
"While the nation has made great strides in reducing drunk driving over the years, it continues to be one of the leading causes of death and injury on America's roads — claiming a life every 48 minutes," added David Strickland, the agency's administrator, in a prepared statement.