A government study released on Wednesday has found about 15 percent of the U.S. adults have driven under the influence of alcohol in the past year.

Another 4.7 percent of the drivers were discovered to be under the influence of illegal drugs, according to the survey by the Substance Abuse and Mental Health Services Administration.

Wisconsin is the state with the worst drunken driving rates in the country, with 26.4 percent of adult drivers reported driving under the influence of alcohol in the previous year.

Wisconsin is closely followed by North Dakota with 24.9 percent, Minnesota with 23.5 percent, Nebraska and South Dakota, which round up the top five.

The survey found that Utah had the lowest incidence of drunken driving. Only 10 percent of adult motorists were reported to be driving under the influence.

Arkansas, West Virginia, North Carolina and Kentucky all had drunken driving rates of less than 11 percent.

The study was based on information from the National Survey on Drug Use and Health. 127,283 adults were asked in 2004, 2005 and 2006 whether they had driven under the influence in the past year.

Referring to the fact that the drunken driving rates are higher in the northern states, Eric Goplerud, research professor at George Washington University Medical Center, said that cultural and demographic issues may play an important role in the rates of driving under the influence in certain states. He told the Associated Press that religious issues might have a great significance. For example, religious affiliations in the Southeast often strongly discourage drinking, but that does not happen so much in the upper Midwest.

National Highway Traffic Safety Administration findings show 16,700 people died in accidents related to driving under the influence of alcohol in 2004.