Ten Indiana school districts offered property tax referenda Nov. 8 to finance buildings or budgets. That was the most for a November election since 2010.

More referenda are offered during elections in May, probably because 69 percent of all May referenda have passed since 2010. Only 39 percent of November referenda have passed in that time.

On Nov. 8, nine out of 10 school referenda passed. It was a November surprise. Why did it happen?

There’s a trend. The share of referenda that pass has been going up. Only half of all referenda passed from 2010 to 2013. A bit more than two-thirds passed in 2014 and 2015.

This year it was 17 of 20, 85 percent. Perhaps it’s the economic recovery raising voter incomes. Maybe school districts are running more sophisticated campaigns. Maybe districts are “self-selecting,” so the only districts that try are those that think they can win. Whatever the reason, November’s referenda success continues the trend.

But November’s results may also be due to the features of the school districts proposing the referenda. Let’s invent a scoring system to measure the features of districts that pass referenda.

First, score some things that school districts can’t really control.

Give one point if income per person in the school district’s county is above $34,000. If incomes are lower, the district’s voters may lack the ability to pay higher property taxes. Give one point if the business share of taxable assessed value is more than 50 percent. If businesses pay more, homeowner tax bills are lower. Give one point if the school district is really small, with fewer than 1,000 students. Communities tend to vote yes if they think the district’s survival is at stake.

Take account of two factors that districts can control, at least a little.

Give one point if the referendum adds less than 25 cents per $100 assessed value to the tax rate. Districts can ask for less, but if their budget or building needs are large, or their tax base is small, then the rate will be higher. Add another point if the district’s average SAT score is more than 1000. Successful districts have higher scores, but this also depends on how learning-ready their students are.

Then there are the election factors.

Give a point if the district has tried before. Win or lose, experience helps. Give a point if the district has won before. That’s great evidence that a district can pass a referendum. And add one for holding the referendum in May. Until this month, that seemed to matter.

That’s eight possible points. There have been 148 school referenda since November 2008. Districts had five or more points in 34 of those referenda, and 32 passed. That’s 94 percent, almost a lock.

Thirty-seven districts had four points. About two-thirds of their referenda passed, a good chance to win. Forty-one districts had three points, and about half of those won. That’s a coin flip. The remaining 36 districts had two or fewer points, and eight passed referenda, only 22 percent. Winning is not very likely.

So what happened this November? Seven of the 10 referenda were offered by districts with four, five or six points. They all won. Three had three points. Two won. Gary Community Schools’ referendum lost 51 percent to 49 percent.

The average number of points for these 10 referenda was 4.3. In all the November elections before that, the average was 2.6. The features of the school districts proposing referenda this November pointed towards more success.

The main reason for the improved chances this time, though, was the fact that nine of the 10 districts had tried before. Four had won before. Two were renewing tax rates that had been passed in 2010, so no new added tax was proposed. If a district has tried or won before, then offering a referendum in November seems to be no big disadvantage.

There were other surprises in other elections this November, and some pretty spectacular failures of forecasting efforts.

This scoring system was designed to explain referenda results in the past. Will it predict referenda results in the future? Unlike presidential elections, we don’t have to wait four years to find out. See you in May.

Larry DeBoer is professor of agricultural economics at Purdue University. Send comments to [email protected].