ST. LOUIS — Violent crime has become more deadly in the city of St. Louis over the past decade, according to a new study by researchers from the University of Missouri-St. Louis.

Criminology professor Janet Lauritsen and criminology doctoral candidate Theodore Lentz analyzed years of St. Louis Police Department data and found the number of homicides per robbery or assault has risen by more than 50 percent over the past eight years, from 23 homicides per 1,000 incidents to 36.

The prevalence of gun use in St. Louis is a likely factor, the researchers say. One possibility, Lauritsen said, is that shooters are firing more bullets, or bullets of a higher caliber, and therefore shootings are more deadly than they used to be. It’s also possible, she said, that shooters are more interested in killing their targets now.

“Whatever is driving the use of guns is likely to have more lethal consequences,” she said of the study.

The study highlights gun use and violence in a city working hard to reduce crime and shake a bad national reputation. It also showcases just how difficult crime has been for police to curtail. Homicides in the city remain proportionately higher than in other cities of comparable population size.