Male incentives for long-term commitment in romantic relationships and investment in children are diminished due to the increased availability of female partners. Daniel Kruger

ANN ARBOR—In areas where adult men are scarce, young people are 36 percent more likely to commit assaults, a research team led by the University of Michigan School of Public Health has shown.

The team found that the proportion of the population lacking a high school degree also is associated with the likelihood of violent behaviors of 10-to-24-year-olds. These two factors explain more than two-thirds of the variation in the rate of adolescent assaults.

The study in the Journal of Community Psychology is the first to show a community-level association between the scarcity of adult men and adolescent violence, said Daniel Kruger, research assistant professor at the U-M School of Public Health.

“Father absence is a risk factor for a range of adverse outcomes at the individual level,” he said, adding that behaviors from promiscuity to violence often are found in populations where fathers are absent. “In areas where men are scarce in proportion to women, family dynamics and relationships with women are considerably altered.”

When women outnumber men—who have become scarce because of factors that include job loss, death or incarceration—there are more single-parent, female-led homes and lower marriage rates, Kruger said.

“Male incentives for long-term commitment in romantic relationships and investment in children are diminished due to the increased availability of female partners,” he said.

Kruger and colleagues Sophie Aiyer, Cleo Caldwell and Marc Zimmerman used data from the Flint (Mich.) Police Department to calculate average monthly assault rates and compared it with sociodemographic data from the 2000 U.S. Decennial Census.

Their research adds to other recent work from the Fathers and Sons program, part of the Michigan Youth Violence Prevention Center at the U-M School of Public Health.

This summer, the center released a related study that showed nonresidential fathers who make an effort to be part of their pre-adolescent sons’ lives can help young people avoid violent behaviors.

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