A new study from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington has concluded that more than half of police killings in the U.S. are not reported. According to the research, there were 30,800 deaths caused by police violence between 1980 and 2018. But the official report failed to document more than 55% of the cases.

The data, which shows that racial disparities have remained largely unchanged since 1980, proves that Black people are still disproportionately affected by police violence. 

“All of these statistics really outline the systemic racism that is driving police violence in the U.S.,” researcher Eve Wool said, according to Medical News Today. "Police violence is a public health issue, violence is a public health issue and systemic racism is a public health issue.”

Professor Alexes Harris, a sociologist at the University of Washington in Seattle, said many people have been “hiding behind” the lack of numbers on racial disparities in police violence. 

"This report now calls us to the carpet and asks us what [we are] going to do to address this violence,” Harris said.

The researchers first looked at information from the National Vital Statistics System, a federal database that gathers data from death certificates. The federal database data was then compared to information from organizations that track police killings through news reports and public records requests. 

After comparing the data, researchers said about 55% of fatal police encounters in the past four decades were listed as another cause of death, The New York Times reports. 

“I think the big takeaway is that most people in public health tend to take vital statistics for the U.S. and other countries as the absolute truth, and it turns out, as we show, the vital statistics are missing more than half of the police violence deaths,” Dr. Christopher Murray, director of the IHME, said, according to The New York Times.

Murray said it's important to question why the numbers from open-source investigations aren’t showing up in the official statistics. 

"That does point to the system of medical examiners and the incentives that may exist for them to want to not classify a death as related to police violence,” the director said.

More than 17,000 of the nearly 31,000 Americans killed by the police in the past four decades are unaccounted for in the official statistics, the study concluded. While the study showed that Black Americans were 3.5 times as likely to be killed by police compared to white Americans, Latinos and Native Americans have also suffered higher rates of fatal police violence. 

Oklahoma, Arizona, Alaska and the District of Columbia are the states with the highest rates of police killings, according to the research. Minnesota, which was thrust into the national spotlight after police killed George Floyd in the city of Minneapolis, has one of the lowest rates of police violence.