A half century after the U.S. Surgeon General first warned Americans about the hazards of cigarettes, 8 million lives have been saved by laws, taxes, and incentives designed to curb the deadly habit.

However, while on average tobacco control measures have extended these Americans' lives by two decades, more people than ever are lighting up worldwide, and modest declines in smoking prevalence in the U.S. have leveled off. One in five adult Americans continues to smoke today, and hundreds of thousands of people die annually from smoking-related illnesses, the researchers concluded.

Researchers reported these findings today in the Journal of the American Medical Association . In one study, Theodore R. Holford from the Yale University School of Public Health analyzed actual smoking mortality data from 1964 to 2012. He contrasted it with estimates based on a model that presumed none of the intense anti-tobacco measures ever had been implemented.

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Smoking Deaths 'Inexcusable'

Vince Willmore, vice president of communications for Tobacco-Free Kids, told Healthline that the smoking rate in the U.S. has been slashed by more than half since 1965, from 42.4 percent to 18 percent in 2012, according to the U.S. Centers for Disease Control .

“The fight against tobacco has been one of our nation’s greatest public health achievements, but it is far from over," he said. "Tobacco remains the nation’s number one cause of preventable death and disease, and nearly 44 million American adults still smoke.”

He said it is “inexcusable” that more than 400,000 Americans still die each year from tobacco-related illnesses.

Willmore called on the U.S. Food and Drug Administration to aggressively exercise its powers to regulate tobacco, as well as electronic cigarettes. The federal tobacco tax must be significantly increased, he said. Provisions in the Affordable Care Act that require insurance companies to pay for smoking cessation programs must be enforced, he added.

He noted that only two states—North Dakota and Alaska—fund tobacco prevention and cessation programs at levels recommended by the CDC. “The states this year will collect $25 billion from the tobacco settlement and tobacco taxes, but are spending less than 2 percent of it to fight tobacco use,” Willmore said.

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New Strategies Needed on the State Level

Dr. Jed Rose, director of the Center for Smoking Cessation at Duke University Medical Center, told Healthline that with smoking prevalence plateauing in the U.S., “The measures that worked in the past may not work in the future.”

Ray Niaura, associate director for science at the Schroeder Institute for Tobacco Research and Policy Studies at the American Legacy Foundation, agreed.

“What tends to happen with campaigns of any kind is that there is small, incremental progress, which is good, but when the campaign ends, the progress or the momentum wears off,” he told Healthline. “We know that smoking is pretty strongly associated with being from a disadvantaged economic background or lower education level. How do we reach those smokers with effective messages and strategies? Is it just a matter of educating them, or do we need to do more?”

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Middle-Income Countries Are Tobacco's New Frontier

In a second JAMA report, researchers at the Institute of Health Metrics and Evaluation at the University of Washington in Seattle did a global analysis of smoking trends from 1980 to 2012.

While smoking declined by 25 percent for men and more than 40 percent for women, more people than ever are taking a drag as the earth's population has exploded. Today, almost 1 billion people light up each day. Since 1980, the total number of cigarettes consumed has increased by 26 percent, the researchers found.

In some African countries, as few as 5 percent of women smoke. However, in countries like Indonesia, Armenia, and Russia, more than half of men do. Since 2006, smoking prevalence has spread like wildfire in China, Bangladesh, and Indonesia.

Other countries—including Canada, Mexico, Iceland, and Norway—have seen tremendous decreases of 50 percent or more in smoking prevalence since 1980.

Dr. Christopher Murray, director of the Seattle institute, said tobacco control at the county level “has enormous potential to drive smoking rates even lower.”

Mexico's Success Story

Murray told Healthline that Mexico didn't really make tobacco control a priority until the early 2000s. He said the success of countries like Mexico, which banned tobacco advertising and smoking in public places while launching educational campaigns, shows that it takes a mix of strategies to effectively snuff out smoking.

The authors call for increased tobacco control measures and intense monitoring of the policies' effectiveness. “Although in several countries substantial uncertainty remains in monitoring tobacco exposure and estimating the disease burden associated with it, there can be no doubt that both are large,” they wrote.

Worldwide, countries that have been successful at getting people to quit have taxed tobacco to the hilt and launched sometimes graphic campaigns about the health risks of cigarettes.