The drop continues a decades-long decline that had slowed in recent years.
Dr. Matthew McKenna, director of the CDC's Office on Smoking and Health, said the prevalence of smoking in America is still "much higher than what we've aspired to."
Major reasons for the continuing decline in smoking, McKenna said, include greater public knowledge of its dangers, limitations on tobacco advertising and better information for smokers on how to get help quitting.
"One of the most important things is, with the growing awareness of the dangers of second-hand smoke, there is less and less public smoking taking place," he said. "This creates an environment where it's easier for people who are trying to quit."
The drop in the adult smoking rate to 19.8 percent is the first significant decrease — 1 percentage point — since 2004. It's something of a milestone in a nation with a long love-hate relationship with tobacco.
In 1965, a year after the U.S. Surgeon General issued a landmark report about the health dangers of tobacco, the smoking rate was over 40 percent. It took two decades of health education and government action to bring the rate below 30 percent.
Also in the new CDC report, researchers estimate smoking-related deaths in the first part of this decade. From 2000 to '04, smoking and exposure to smoke resulted in at least 443,000 premature deaths per year from cancer and heart and respiratory diseases.
Much of the news in the report, which is based on a national survey of more than 23,000 people, is good. But the CDC has set a target of 12 percent for adult smoking by 2010.
"It's very unlikely, given these levels, that we'll be able to reach that," McKenna said, adding that he'd like to see public and private health insurance systems cover smoking cessation services more consistently.
A continued, slow decline in smoking is expected for the coming few years, according to David Mendez, a professor at University of Michigan's School of Public Health who developed a model to predict smoking rates.
"The influx of smokers is less than the outflow of smokers, so as long as that continues, the rates are going to keep falling, albeit at a very slow rate," Mendez says.
In 2007, more than 43 million adults were smokers, and more than three-quarters of them smoked every day.
While smoking has declined for all groups studied over the past 40 years, some groups still smoke significantly more than others.
More than one-third of American Indian/Alaska Natives smoked in 2007, for example. Meanwhile, smoking rates among African American women have dropped to 16 percent. There are more disparities along gender, ethnic and economic lines.
Higher cigarette prices and the diminishing number of public places where it's permissible to smoke may be driving more smokers to try — and ultimately to succeed at — quitting cigarettes, says Matthew Farrelly, senior director of the Public Health Policy Research Program at RTI International, a nonprofit research firm in North Carolina.
Also, more than half the population is now covered by a state or local smoke-free workplace law, according to the American Nonsmokers' Rights Foundation. Farrelly says the percentage was in the single digits just six years ago.
"When a workplace goes smoke-free, people cut back on the amount they smoke, and some people quit," Farrelly says. [via npr]