The smoking rate among U.S. adults has been falling steadily for decades but the latest survey from the Centers for Disease Control and Prevention finds the 2015 decline is the biggest in more than 20 years.

According to WILX-TV 10, smoking is the nation's leading cause of preventable illness and the CDC estimates it causes more than 480,000 U.S. deaths each year.

The government report says the rate of smoking among adults in the U.S. fell two percent, to 15 percent last year, from 17 percent in 2014.