I'm not surprised that societies that believe in eternal punishment have lower crime rates. For then what you do while alive is not just a matter of getting away with it, because there's no escaping Divine Judgement.
The study, appearing in the Public Library of Science journal PLoS ONE, found that criminal activity is higher in societies where people’s religious beliefs contain a strong punitive component than in places where religious beliefs are more benevolent. A country where many more people believe in heaven than in hell, for example, is likely to have a much higher crime rate than one where these beliefs are about equal. The finding surfaced from a comprehensive analysis of 26 years of data involving 143,197 people in 67 countries.
“The key finding is that, controlling for each other, a nation’s rate of belief in hell predicts lower crime rates, but the nation’s rate of belief in heaven predicts higher crime rates, and these are strong effects,” said Azim F. Shariff, professor of psychology and director of the Culture and Morality Lab at the UO. “I think it’s an important clue about the differential effects of supernatural punishment and supernatural benevolence. The finding is consistent with controlled research we’ve done in the lab, but here shows a powerful ‘real world’ effect on something that really affects people—crime.”
Last year, in the International Journal for the Psychology of Religion, Shariff reported that undergraduate students were more likely to cheat when they believe in a forgiving God than a punishing God.
I believe in both Heaven and Hell, and a forgiving God, who can only forgive when forgiveness is asked. If it's not asked for, then He has no choice but to be a punishing God, because justice demands it.
To be certain of forgiveness, a person must confess their sins to a priest. There's nothing like it to make you feel* totally clean, and like a totally new person. Especially if your sins have been weighing you down over the years. After confessing completely, it's far less likely that a person will offend as gravely again.
Related link: Study: Belief in Hell is associated with reduced crime
*Feeling that you are forgiven is not necessary. For God gave us the Sacrament so we would know that we are forgiven, especially as feelings can be deceptive. However, feelings can be given as a gift, and some are just amazing. While as at most other times, no feeling what so ever.