For the first time since record keeping began 50 years ago, the number of Americans who smoke cigarettes has dropped below 40 million.

The Centers for Disease Control and Prevention reports that between 2005 and 2015, the percentage of cigarette smokers declined to 15 percent from 21 percent. There were significant reductions in smoking across all ages, races and ethnicities, socioeconomic levels and regions of the country.

In 2005, there were 45.1 million smokers in the country. By 2015 there were 36.5 million.

Sixteen percent of men and 14 percent of women smoked in 2015, down from 24 percent and 17 percent in 2005.

Smoking declined most sharply in the youngest age groups. But 13 percent of 18- to 24-year-olds, 18 percent of 25- to 44-year-olds, 17 percent of 45- to 64-year-olds, and 9 percent of those over 65 were still smoking.