Sending bar patrons home at earlier hours may lower the rate of late-night violence, hints a new study from Australia.

In the city of Newcastle, New South Wales, home to about half a million people, researchers found that bumping up the closing time for a group of downtown pubs led to a reduction of more than a third in local police-recorded assaults.

There is considerable debate about the effect of restricting licensed premises trading hours, researcher Craig Jones of the New South Wales Bureau of Crime Statistics and Research told Reuters Health in an email.

Those with a vested interest in keeping late trading -- the alcohol industry -- argue that closing pubs early will hurt the industry while doing nothing to reduce alcohol-related harm. The best research evidence would suggest the opposite but most of this evidence comes from studies that have examined the effect of extending trading hours, Jones said.

Few studies, he added, have examined the impact of restricting trading hours, mainly because the post-WWII trend has been toward more liberalized trading in alcohol.

Jones and his colleagues recently encountered a natural experiment that could potentially fill in that gap. In 2008, the government revised the mandatory closing time from 5 a.m. to 3 a.m. in Newcastle. A compromise quickly watered this down to 3:30 a.m.

The team also identified a similar nightlife district in the nearby city of Hamilton that did not undergo any closing time changes. This allowed them to compare before and after assault rates while taking into account other factors that may influence violence, such as a troubled economy or bad weather.

Based on police records between January 2001 and September 2009, they found the restricted trading hours in 2008 resulted in a 37 percent drop-off in assaults occurring between 10 p.m. and 6 a.m., or a total of about 132 fewer assaults per year.

Jones noted that the actual number of assaults prevented by the restrictions is likely even greater, given that only around one in three assaults are reported to the police.

There were no changes in Hamilton's nighttime assault rates, report the researchers in the journal Addiction, which suggests that the government-imposed restrictions were responsible for the results and that there was no displacement of the violence.

Tim Stockwell, Director of the Center for Addictions Research of British Columbia at the University of Victoria, said the findings are consistent with his own similar research.

What is striking about this new study is that regulatory authorities are beginning to turn the tide in the other direction, he told Reuters Health in an email. An era of deregulation of the liquor market is beginning to be wound back toward tighter restrictions in response to community concern about alcohol-related violence.

Last call varies widely around the U.S. While Salt Lake City turns off its taps at 1 a.m., bartenders along the Jersey Shore and in some parts of Alaska can keep pouring until 5 a.m. And in Memphis and Las Vegas, you can listen to live music or play poker with a pint in hand all night.

As for New York City, Jason Post, spokesman for New York City Mayor Michael Bloomberg, told Reuters Health: New York has always been the City that never sleeps. We don't have plans to limit that.

The city of Seattle currently restricts bars from being open past 2 a.m. However, ongoing violence apparently triggered by intoxicated people flooding the streets at closing time has sparked discussion around an opposite strategy to Newcastle's: extending last calls to 4 a.m., or even keeping bars open 24 hours. Some also advocate staggering closing times.

The logic of preventing people spilling out onto the streets at exactly the same time can be applied in the other direction: shortening trading hours of some venues, possibly those with the worst track record for violence, noted Stockwell. In most cities, it has been shown that a small minority of bars, about 10 percent, contribute two thirds of night-time violent incidents.

At around the same time that last call restrictions were imposed in Newcastle, New South Wales published a top 100 list of the pubs with the largest number of assaults. The researchers note that such bad publicity could have also motivated pubs to modify their service to reduce assault rates. However, since Hamilton was also represented on the list, they note that it should not have influenced their findings.

Nobody is arguing for a new temperance movement and ultimately it is a decision for policy-makers to get the mix right, Jones said. But I think it would be unwise to believe those who suggest that restricting or liberalizing trading hours will have no effect on alcohol-related crime.

While states and cities continue to work on the best strategy to keep its streets safe, Stockwell offers some advice: If you are concerned about not feeling safe late at night or during the early hours of the morning in your city or town, then you might consider writing to civic authorities or your member of parliament encouraging them to restrict trading hours.