Although smoking rates have declined over the past few decades, cigarettes continue to cause about three in 10 cancer deaths in the United States, according to a research published in the Annals of Epidemiology.

The study, which was conducted by the American Cancer Society, calls for new efforts to reduce smoking prevalence to help prevent future cancer deaths, according to a press release on the organization’s website.

Lead author Eric J. Jacobs and his team analyzed data on smoking rates from the National Health Interview Survey, as well as data on the risks of smoking from epidemiologic studies, to estimate the proportion of U.S. cancer deaths caused by smoking— what the researchers called the population attributable fraction (PAF).

The researchers looked at deaths from the 12 cancers formally linked to smoking by the U.S. surgeon general and they observed that the PAF was 28.7 percent. But after factoring in cancer deaths than may have been caused by smoking, the PAF was 31.7 percent, according to the news release. These estimates don’t factor in other potential cancer deaths caused by secondhand smoke or other kinds of smoking such as cigars, pipes or smokeless tobacco. Study authors only considered cancer deaths caused by smoking cigarettes.

According to the news release, the last PAF estimate for smoking was calculated more than 30 years ago, when famed British researchers Richard Doll and Richard Peto observed that 30 percent of all cancer deaths in the U.S. were caused by smoking.

While there has been a decline in smoking prevalence, the current PAF and previous estimate may be similar because of the addition of new cancers that may be caused by smoking, as well as an increase in lung cancer deaths among female smokers and a greater focus on reducing deaths from cancer caused by factors other than smoking.

However, efforts to reduce smoking haven’t been futile, the authors noted. According to the Centers for Disease Control and Prevention (CDC), more than 40 percent of Americans smoked in the 1960s, but today, only 18 percent of Americans smoke.