The debate over Iowa City’s 21-ordinance is one of those issues that just won’t die — we keep having the same conversations over and over again. This latest round of voting, which will occur on Nov. 5, was brought about by a petition filed against the law by the owner of the Union Bar and a manager at Martinis.

The ordinance prohibits anyone under the age of 21 from being in the bars past 10 pm. The 21-ordinance exempts establishments that have music shows past midnight and restaurants that receive at least half of all sales from goods and services other than alcohol.

Most recently, the Iowa City government released some illuminating data on crime trends in periods before and after the ordinance passed in 2010.

We’re not saying that the 21-ordinance directly affected the changes, and the report itself drew no such conclusions, but the information it provides seems to suggest that repealing the 21-only ordinance would be a mistake. There is little reason to remove an ordinance that has been extremely effective at best, or minimally effective at worst, in reducing underage drinking.

Calls requesting service from the police in cases of intoxication, fights, loud parties, assault, rape, and other crimes have fallen substantially between the 2007-2010 and the 2010-2013 periods across the University Impact Area (which includes downtown). Theft is the only instance in which calls to the police have risen.

This isn’t terribly surprising. Opponents of the 21-ordinance often argue that drinking will just migrate from bars downtown to rowdier house parties in other neighborhoods.

However, if that were the case, you’d expect calls to the police reporting loud parties to increase, but they’ve fallen by 7 percent. In fact, calls reporting crime (except for theft) around the entire city have fallen since the 21-only ordinance passed.

This report also found a 23.6 percent reduction in emergency medical responses downtown, a flat response rate off-campus, and a 9.3 percent growth in responses across the city.

It may be tempting to say this change is due to a growing prevalence of parties, and there may be some truth to that. However, this could be caused by other factors, such as population growth.

Drinking among students at the university has also declined. The National Collegiate Health Assessment found that from 2009 to 2013 (no data were collected the year the 21-ordinance passed in 2010), the number of UI students who drank alcohol in the past 30 days fell by 10 percentage points, the average number of drinks consumed per party has fallen by 20 percentage points, and risky drinking in the past two weeks fell by 11 percentage points.

As with the police and emergency-call data, this can’t be directly linked to the 21-ordinance per se. Society is a complex organism — there are always many interrelated events going on that can influence one another.

Nevertheless, these are all generally positive changes, and the City Council has been reasonable in exempting establishments from the 21-ordinance that do more than simply profit from getting students drunk.

Iowa City’s alcohol situation is a blight upon its otherwise stellar reputation. Eliminating the 21-ordinance threatens to undo the past few years of progress against the university and city’s drinking problem.