03/16/2011 10:10 am ET | Updated May 25, 2011

Smoking Rates: Pack-A-Day Smoking Is Down Dramatically

Over the last 40 years, the number of people who smoke a pack a day has dropped significantly, a new study finds. And California -- with its comprehensive anti-smoking efforts -- has led the charge.

The report, published yesterday in JAMA, tracked the prevalence of heavy smokers (defined as people who smoke 20 cigarettes or more, per day) among more than a million-and-a-half respondents between 1965 and 2007.

Researchers from the University of California San Diego found that in 1965 -- the year after the first-ever surgeon general's report on smoking and health -- 56 percent of people who identified as smokers were heavy, or pack-a-day, smokers. By 2007, that percentage dropped dramatically, to only 40 percent.

In California, the decrease was even more pronounced; less than a quarter of people in 2007 responded that they were heavy smokers.

The prevalence of moderate-intensity smokers (defined as people who smoke 10 or more cigarettes per day) also fell.

Researchers say that the decline in pack-a-day smokers in the U.S. is directly reflected in the declines in lung cancer deaths, nationwide. They also stress the data shows that public policies aimed at decreasing smoking are effective, which is why in California in particular, both the prevalence and intensity of smoking have fallen. And with continued effort, they should keep on falling.

"Among younger birth cohorts," the study's authors wrote, "only a small minority of the population is expected to ever attain cigarette consumption levels of even 10 or more cigarettes per day."