Pity the upper Midwestern motorist – or, rather, the poor pedestrian that crosses his bleary-eyed path. According to a story on FOX News:
The upper Midwest has the worst drunken driving rates in the country, according to a government report that says 15 percent of adult drivers nationally report driving under the influence of alcohol in the previous year.
Wisconsin leads the way. The federal government estimates more than a quarter of the state’s adult drivers had driven under the influence. Rounding out the worst five are North Dakota, Minnesota, Nebraska and South Dakota.”
From Minnesota (MPR) to Florida (the Palm Beach Post), and along with the national news services like the Associated Press (“Study: Midwest has the worst drunken driving rates”), Lake Wobegon turned into Lake Woebegone. Naturally, this required a sociological explanation. As the AP reported:
Eric Goplerud, research professor at George Washington University Medical Center, said cultural and demographic issues probably have a role in the higher rates of driving under the influence in certain states. He said that religious affiliations in the Southeast often strongly discourage drinking, but that doesn’t occur so much in the upper Midwest. ‘A good part of the social life is around drinking,’”
The Milwaukee Sentinel Journal, on the other hand, just needed someone to explain why the findings required no explanation:
‘I’m not shocked, I’m not surprised,’ Nina J. Emerson, director of the Resource Center on Impaired Driving at the University of Wisconsin Law School, said of the latest report.
Nor did the finding startle Paul Moberg, senior scientist in the Population Health Institute at UW-Madison and co-author of a 2007 study on Wisconsin’s alcohol and drug use patterns.
‘Not really,’ he said. ‘I think that’s been what we’ve seen historically.’”
But did the government study really find what all the media accounts claimed it did?
The Substance Abuse and Mental Health Services Administration (SAMHSA), which is part of the Department of Health and Human Services, surveyed 127,283 drivers nationwide over the course of 2004, 2005, and 2006. And it describes the results as a measure of “driving under the influence of alcohol.”
Most people would assume (as many journalists did) that this refers to the proportion of drivers who were legally DUI, e.g., had blood alcohol levels (BAC) of .08 or more, the level at which they are legally intoxicated. But SAMHSA uses the phrase “driving under the influence” to mean having any measurable level of alcohol in the blood.
The problem with this approach is that it conflates legal with illegal drink driving – the person who has a drink after work and who has a BAC lower than 0.8 and the person who shouldn’t be in the driving seat.
Does it make sense to do this? If you assume that any amount of alcohol consumption should prohibit driving, then yes. This would mean that the presumptive level for intoxication should be set at .01 BAC. But that assumption runs counter to the research on BAC levels.
The National Highway Traffic Safety Administration (NHTSA), in its July 2001 report “Legislative History of .08 Per Se Laws” found that while the risk of being in a crash gradually increases at each BAC level, there was little difference in relative risk for drivers with BAC levels between zero and .05 This risk, however, rises very rapidly after a driver reaches or exceeds .08. This report also states that:
A BAC of .08 is a reasonable level at which to set the illegal limit. A .08 BAC is not typically reached with a couple of beers after work, or a glass or two of wine with dinner. The average 170 pound male would have to consume more than four 12 oz. cans of beer within 1 hour on an empty stomach to reach .08 BAC. The average 137 pound female would need at least three cans of beer in one hour on an empty stomach to reach that level.”
SAMHSA’s survey method, on the other hand, suggests that people who have a glass of wine at dinner are drunk driving if they get behind the wheel afterwards. (It should be noted that a BAC of .05 – or very roughly, the level produced by drinking two standard measures if sober – is favored by many other countries as the legal cut-off point).
Many of the news reports on the SAMHSA study also linked the results to the rate of alcohol-related traffic crashes and fatalities. Yet data from the NHTSA shows that 85% of all alcohol-related traffic fatalities in 2006 involved drivers with a BAC of .08 and higher, and 58% with a BAC of .15% or higher – the so-called incorrigible group of “hardcore drunk drivers” who cause havoc on our roads.
When providing statistics to guide public safety, making such distinctions are important – in this case, it’s the difference between doing something legal and doing something illegal. The upper Midwest may not be off the hook on drink driving for historical and sociological reasons, but it can’t be judged guilty on the basis of SAMHSA’s stats.