A new study that zeroed in on a single city in Michigan found that where men are scarce, youth were more likely to commit assaults.

Researchers from the University of Michigan analyzed youth arrests and U.S. Census Bureau data for Flint, Mich., an industrial city whose fortunes have risen and fallen with General Motors Corp.

They found that “adult male scarcity” – a low ratio of adult men to women – was closely tied to the share of households that had meager incomes or were getting government assistance, as well as the share of single parents.

But a lack of men also seems to have added effects of its own, beyond its ties to poverty and family structure. Even after controlling for other kinds of disadvantages, male scarcity explained 36% of the difference in youth assault rates from census tract to census tract, researchers found.


“Male scarcity is actually a driver of conditions,” said Daniel Kruger, research assistant professor at the University of Michigan and one of the authors of the study. “It’s the most powerful predictor.”

When education is factored in, it becomes an even more powerful predictor: Male scarcity, plus the percentage of people with less than a high school degree, explained 69% of the difference in youth assault rates, the study found.

Researchers tied the shortage of men to a slew of other troubles: Nationally, men have been more likely to lose jobs than women in recent decades, possibly pulling them away from Flint. Men are also at higher risk of dying from accidents, violence and some diseases, and those differences are bigger in poorer and less-educated communities. On top of that, high incarceration rates pull men away.

Based on the results, researchers suggested that strengthening relationships with fathers and adult male role models could help cut down on youth crime. Kruger said the study offered evidence that a scarcity of men, already known to shape marriage and relationships, also affected communities in other ways.


“When we look at population trends, not just in Flint but around the world, we see that the sex ratio really shapes a lot in our social world,” he said.

The study, published online this month in the Journal of Community Psychology, was based on assault rates for people ages 10 to 24 between June 2006 and 2008, as well as data from the 2000 U.S. Census.

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