The report did not include teens. About 16 percent of high school students were smokers in 2011, according to an earlier CDC report.
Patrick Reynolds, executive director of the Foundation for a SmokeFree America, told The Associated Press that he was elated that the adult smoking rate, for years at about 20 percent, had dropped below that longstanding plateau.
He said factors he thinks have contributed to fewer adults smoking include rising state and federal tobacco taxes, more spending on prevention and cessation programs, and more laws banning smoking in public.
"This is a real decline in smoking in America. I'm ecstatic about it. It's proof that we are winning the battle against tobacco," he said by telephone from Los Angeles.
CDC report: http://www.cdc.gov/nchs/