Zero tolerance, zero effect

As college administrators, social scientists and law enforcement officials across the country continue to debate whether the drinking age should be 18 instead of 21, a Sam Houston State University economist challenges a related law: the “zero tolerance” policy.

Darren Grant says zero tolerance laws have zero effect.

In a paper forthcoming in the journal Economic Inquiry, he analyzed data from 30,000 fatalities in nighttime accidents involving drivers under 21.

“Both in terms of the number of accidents and the blood alcohol of the drivers in those accidents, the research consistently showed that zero tolerance laws had no effect,” Grant said. “Other factors matter, but not these laws.”

Zero tolerance laws became prevalent during the 1990s, when the U.S. Congress threatened to withhold highway funding from states that didn't comply.

Grant says the logic behind zero tolerance laws is suspect.

“The idea was, since drivers under 21 are not supposed to be drinking, you should be guilty of drunk driving if you are caught driving with any amount of alcohol in your system,” Grant said.

“Because you must sacrifice more to comply with the law, we should expect some people will just give up trying to satisfy the law and drink more,” he said.

But Grant found this did not happen.

“Instead, among drivers involved in traffic accidents, there is the same fraction of heavy drinkers, the same fraction of mild drinkers, the same fraction of nondrinkers,” he said. “It's just not changing.”

Grant also compared the blood alcohol distributions of involved drivers in the two years before zero tolerance laws were established in each state, and again in the two years after. The two distributions were also virtually identical.

“That's a sign that this law is essentially inert; if it's affecting the amount of drinking that people do, these distributions should look different,” he said. Grant's colleague at Sam Houston State and fellow economist, Donald Freeman, completed a similar study in 2007 that yielded similar results regarding a related law that lowered the allowable blood alcohol limit for adult drivers. That paper was published in the journal Contemporary Economic Policy.