Juvenile assault and drug-related arrests on Oahu declined during the 2009-2010 school year when Hawaii furloughed teachers and canceled classes on 17 Fridays to save money during the economic downturn, a University of Hawaii economist said Thursday.

The results confirm research by other scholars showing assaults by juveniles tend to drop when school’s not in session.

"When students are in one enclosed space together, certain crimes become easier. Fights are one of them," said Timothy Halliday, an associate professor of economics at the Manoa campus.

An analysis of Hono­lulu Police Department data by Halliday and two other economists showed police made 1.2 fewer juvenile arrests for assault for each "Furlough Friday," compared with typical Fridays when school would have been in session. For each Friday when teachers were furloughed, police made slightly fewer than one juvenile arrest for drug-related crimes.

This translated to about 20 fewer assault arrests and 14 fewer drug-related arrests for the entire shortened school year.

Halliday said he wasn’t aware of other studies showing drops in drug-related crimes when school is not in session. Halliday and his colleagues’ research also differs from previous studies in that assault arrests declined more sharply on Hawaii’s furlough days than in other instances of canceled classes.

There was some regional variation. The drop in assault arrests was most dramatic in Leeward and Central Oahu, while drug-related arrests fell primarily in urban Hono­lulu and Windward Oahu.

The results appear in a working paper Halliday and his co-authors — Randall Akee and Sally Kwak — aim to publish.

The economists don’t attempt to suggest how their analysis could be used to prevent crime in schools. Halliday said he was only "an ivory tower academic" who crunched some numbers.

Instead, he suggested it would be better for administrators, teachers and lawmakers to discuss ways to prevent crime when school is in session.

"I think you need to bring in the people who are actually teaching and doing things to tell you what the problems are and what challenges they’re facing," he said. "Then they can come up with some viable policies that might work."