The 2020 Stockholm Prizes in Criminology have been awarded to Philip Cook of Duke University and Franklin Zimring of the University of California at Berkeley for their “evidence-based explanations of gun policy effects.”

The announcement said that their research “has considerably improved our ability to fight global gun violence. For over five decades, their evidence-based approach has illuminated gun policy effects, stimulating policy initiatives to limit gun violence in many if not all jurisdictions.

“While (Cook) is an economist and (Zimring) is a lawyer, both have been influential in developing and applying the science of criminology.”

The Stockholm announcement cited “steadily rising gun homicides, suicides and accidents,” saying that more than 251,000 people worldwide died from gun injuries in 2016, up 20 percent from 209,000 in 1990.

More people in the U.S. die from guns than from vehicle collisions, and the worldwide supply of guns exceeds one billion, 85 percent of them privately owned.

Cook and Zimring helped develop evidence that gun availability is related to the volume of gun injuries. The announcement said that the researchers’ “influence has guided an entire generation of gun injury scholarship, strengthening the evidence for governments to take more effective action against the massive suffering caused by guns.”

In the 1960s, Zimring and colleagues demonstrated that assaults with different kinds of weapons produced vastly different rates of death per attack. Zimring showed the vast differences in death rates between knives, rifles, pistols and shotguns. He compiled cross-national data to show that murder rates varied more in relation to gun availability than to crime rates.

In his 1999 book “Crime is Not the Problem,” Zimring said that the violent attack rate in England was much higher than in the U.S. but that the death rate from violent attacks was much higher in the U.S., which has a vast gun supply in private hands, compared to the tiny proportion of English people who own guns.

In the 1970s, Cook compared measures of gun availability across the 50 states. By demonstrating that the percentage of suicides committed with guns was a strong correlate of the gun supply in each state, he created a standard measure for predicting variation in lethal gun violence by levels of gun density, the Stockholm announcement said.

This measure predicted different rates at which people die in robberies across different states. His measure is widely used by other scientists to study a range of phenomena, including rates at which police shoot people to death.