The results of the latest national health survey by the government show the percentage of smokers in the United States dropped to 18 percent in 2012.
The nation's smoking rate generally has been falling for decades, but had seemed to stall at around 20 to 21 percent for about seven years. In 2011, the rate fell to 19 percent, but that might have been a statistical blip.
A spokesman for the Centers for Disease Control and Prevention says health officials are analyzing the 2012 findings and have not yet concluded why the rate dropped.
Smoking is the leading cause of preventable illness and death in the United States. It's responsible for the majority of lung cancer deaths and is a deadly factor in heart attacks and a variety of other illnesses.
The CDC launched a graphic anti-smoking advertising campaign last year