The rate at which Americans died from firearm injuries increased by 14% from 2015 to 2017, according to a new study released this week. Since 1999, 612,310 Americans died from firearm injuries that were either due to suicide, homicide, accidental or of some other undetermined cause. Nearly one-fifth of those deaths happened in just those last three years.

The study, published in the latest issue of Health Affairs, a peer-reviewed journal, by a team led by University of Michigan researchers, used data from the Centers for Disease Control and Prevention. Jason Goldstick, a research assistant professor of emergency medicine at the U. of M.’s medical school who led the analysis, said the data revealed “a worsening epidemic of firearm mortality.”

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There were dramatically different rates of firearm mortalities across the U.S. From 1999 to 2017, firearm deaths increased by over 20% in some states, but others saw declines. New York, California and Washington, D.C., which have relatively stricter gun-control laws, had declines in firearm deaths. Arizona and Nevada joined those three jurisdictions in seeing firearm deaths decline in that period.

Men experienced a greater increase in firearm deaths than women, and Hispanic whites — American citizens who are racially white and of Hispanic descent and/or speak Spanish natively — were the only racial/ethnic group that saw reductions in firearm mortality, while firearm mortality rates among both non-Hispanic whites and African-Americans “increased significantly,” the study said.

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These trends in firearm deaths have implications for prevention, particularly in relation to how gun-control legislation should be enacted, Goldstick said. “For instance, suicide remains the most common mechanism of firearm mortality in most states,” and prevention efforts could focus on the highest-risk groups for suicide, such as older males and adults in rural areas, he added.

To help reduce the number of female fatalities, the researchers recommended restricting firearm access among domestic-violence offenders and people convicted of violent crimes. To address suicides and unintentional deaths by firearms among young people, they suggested reducing access to firearms among children.

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Three-quarters of all U.S. murders in 2017 (14,542 out of 19,510) involved a firearm, according to separate analysis by the Pew Research Center; 51% of all suicides that year (23,854 of 47,173) involved a gun. Six in 10 gun-related deaths were suicides (23,854), while 37% were murders (14,542). The rest were unintentional (486), involved law enforcement (553) or had unknown causes (338).

Pew noted one bright spot in the statistics related to gun deaths: While 2017 saw the highest total number of gun deaths in the U.S., “on a per capita basis, there were 12 gun deaths per 100,000 people in 2017 — the highest rate in more than two decades, but still well below the 16.3 gun deaths per 100,000 people in 1974, the highest rate in the CDC’s online database,” the think tank said.