According to FBI data, the United States is becoming safer nearly every year. From 1992 to 2012 (the most recent year for which data are available), the U.S. violent crime rate fell by almost half. Just since 2007, the nation’s violent crime rate has declined from 471.8 to 386.9 incidents per 100,000 people.

But some areas have seen an increase in violent crime (which includes murder, rape, robbery, and aggravated assault). In many of the metro areas where crime rose the most, the economy has been especially strong. This is the case with Odessa, Texas, an oil boom town that has experienced rapid economic growth and large inflows of people. Two other metro areas, Columbus, Indiana, and Sioux Falls, South Dakota, have also experienced strong growth in recent years.

One of the hidden factors that could be driving up crime rates in areas with thriving economies may be shifting local demographics, explained John Roman, senior fellow at the Urban Institute. “The biggest predictor of committing a criminal act is being young, male and relatively low-skilled. And when you have these big natural resource booms, you’re attracting lots and lots of those people to your community.”