Of the many controversies associated with the City Council’s recent decision to enact a 21-only ordinance in Iowa City, none has been greater than questions about the new ordinance’s effect on UI student drinking.

Will restricting patrons of Iowa City bars to persons who are 21 or older reduce alcohol consumption by underage drinkers? Will binge drinking rates at the UI, now among the highest in the country, decrease to levels closer to other universities in the Big Ten? Or will the 21-only ordinance mean that students will simply transfer the drinking habits they honed in Iowa City bars to a vastly enhanced supply of Iowa City house parties? Our answers to these three key questions are, respectively, yes, yes, and no. They are all based on a single essential concept: access.

There is substantial, growing research and survey literature that shows convincingly that reducing access to alcohol reduces alcohol consumption and its effects, especially in young people. Perhaps the most dramatic demonstration of this effect is found in data from regional and national surveys of drunk-driving, alcohol-related injuries and alcohol-related deaths before and after passage of state and national legislation in the early 1980s that raised the U.S. legal drinking age from 18 to 21.

The legislation resulted in substantial reductions — between 10 and 20 percent — in drunk-driving arrests, serious injuries from automobile accidents, and deaths from automobile accidents among U.S. 18- to 21-year-olds. As a result, to date, thousands of young lives have been saved, and tens of thousands of disabling injuries have been prevented.

In the same fashion, research has shown that when zoning ordinances restrict the number of bars and liquor stores in an area, alcohol consumption goes down because access to alcohol is diminished. When prices for alcohol are raised by increasing tax rates, alcohol consumption decreases. When there is more rigorous enforcement of the laws prohibiting underage drinkers from entering alcohol establishments or from consuming alcohol in those establishments, alcohol consumption is reduced. All of these changes reflect reductions in access to alcohol, thereby reducing alcohol consumption.

Many people in Iowa City subscribe to a “hydraulic theory of access,” which assumes that if access to downtown bars is restricted, underage UI drinkers will simply find another way to drink as they have been drinking. That’s where house parties come in. If drinkers are denied entry to the bars, where they have enjoyed easy access to alcohol, so the hydraulic theory goes, they will begin to patronize house parties, which will spring up to meet their needs. We don’t think so.

Seeking, finding, then attending a house party is much more difficult than walking to the Pedestrian Mall and entering a bar. For this reason, access to alcohol by UI students will be substantially diminished. It will be harder — much harder — to maintain a desired quantity and frequency of alcohol consumption. Moreover, house-party attendees will have to consider the risks of attending house parties, which the police have vowed to monitor very closely.

It is also the case that potential hosts of house parties will have to weigh the risks of hosting such events against the distinct possibility that they could be arrested for serving alcohol to underage drinkers, putting their patrons at risk of injury or overconsumption, and running a party that gets out of control.

My expectation is that while there will be some potential house-party hosts who will run these risks, many will not. Accordingly, I don’t see much of an increase in house-party numbers over the year immediately following enactment of the 21-only ordinance in early June.

While many students will doubtless lament the effect of the City Council action on the quality of their extracurricular lives, I applaud the action because, by restricting access to alcohol for underage UI students, the City Council is saving lives, academic careers, and the futures of hundreds of our students.

Peter Nathan is a former UI provost and an expert on alcoholism. Anne Helene Skinstad is a UI clinical associate professor of community and behavioral health.