A government report says the smoking rate for U.S. adults dipped below 18 percent for the first time last year.

That's still about the same rate found in 2012, and translates to about 42 million smokers.

The Centers for Disease Control and Prevention released the findings Wednesday. Smoking was more common in certain groups, like the poor, less educated, and gays and bisexuals.

The nation's smoking rate had stalled at around 20 to 21 percent, until it started dropping a bit a few years ago. In last year's survey, 17.8 percent of adults described themselves as smokers.

Smoking is the nation's leading cause of preventable illness. It's responsible for the majority of lung cancer deaths and is a factor in heart attacks and a variety of other illnesses.