Study finds smokers aren't puffing away as much as they once did.
The days of chain smoking are over for many.
A new study out of the University of California San Diego finds the prevalence of heavy smoking, defined here as a pack a day, has declined dramatically over the past 40 years.
The impact was most notable in California.
Between 1965 and 2007 it dropped from over a quarter of the population to just two percent.
Nationwide in 2007, about seven percent of smokers went through at least a pack of cigarettes a day, down from a quarter of smokers in the 1960s.
Researchers attribute the decline in part to higher cigarette taxes.
It's not just that smokers are quitting or cutting back.
It appears younger generations have been changing their smoking habits.
"A lot of this drop in pack a day smoking has come from young people never reaching the level of even half a pack a day," says Dr. John Pierce.
That trend may be changing.
Last year a University of Michigan study found the decline in teen smoking had plateaued and suggested younger teens may be lighting up more often.
Whether it's one or 20 cigarettes a day, smoking remains the most preventable cause of death in the country.
According to the Centers for Disease Control about 21-percent of adults in this country are smokers.