Smoking rates among U.S. adults remained stalled in 2008, halting the nation’s efforts to cut tobacco use, a government study reports.

The study by the Centers for Disease Control, released in advance of the annual Great American Smokeout, found that 46 million Americans, or about 20.6%, were current cigarette smokers in 2008. That was virtually unchanged since 2004, when 20.9% of adults said they were smokers.

As in previous studies, the CDC noted a correlation between smoking and education levels. In 2008, 41.3% of persons with a general education development certificate smoked cigarettes, compared to 5.7% percent of persons with a graduate degree.

Among states, smoking prevalence was highest in West Virginia (26.6%), Indiana (26.1%) and Kentucky (25.3% percent) and lowest in Utah (9.2%), California (14%) and New Jersey (14.8%).

Smoking is the leading preventable cause of death, killing more than 443,000 people a year and costing the nation $96 billion in health care costs annually, says the CDC, part of the U.S. Department Of Health And Human Services.