Police officers in 2016 were twice as likely to be shot in states that don’t require background checks on all handgun sales than they were in states that do, according to new data from gun control advocacy group Everytown for Gun Safety.

The fatal shooting of a police officer in Tacoma, Washington, on Wednesday marked the 200th shooting of law enforcement officers this year, according to Everytown, which shared its data with The Huffington Post. Fifty-six officers have been killed and 203 have been injured in these 200 shootings.

Sixty-nine of these shootings have taken place in states with background-check laws on all handgun sales. These states employ 337,679 full-time sworn police officers. In states without these laws, which employ 299,355 officers, there have been 131 shootings of law enforcement officers.

Twenty-one of the 25 states with the highest number of shooting incidents per police officer don’t have background checks on all handgun sales, a HuffPost analysis shows.

Seventy-five percent of the firearms used in this year’s police shootings ― 151 total guns ― were handguns.

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“Day and night, police officers run toward danger to keep the rest of us safe, and this tragic milestone is a sobering reminder of the risks they face,” said John Feinblatt, Everytown’s president. “We have to reduce those risks, and data shows that we can ― by making it harder for criminals to get guns. It’s long past time to close the dangerous loophole in our laws that lets criminals buy guns with no background check and no questions asked.”

Federal law requires licensed gun dealers to perform background checks on prospective buyers. It does not, however, require unlicensed gun dealers — typically those who sell their goods at gun shows or online — to perform background checks.

Only eight states require “universal” background checks for all gun purchases. A total of 18 states currently require background checks for all handgun sales, including from private unlicensed dealers. Nevada is slated to become the 19th, as voters there narrowly approved a series of gun control ballot initiatives last month.

Everytown’s data supports the group’s previous findings that law enforcement officers in states that require background checks for unlicensed sales of handguns are 48 percent less likely to be killed with handguns than officers in other states.

The group’s findings also align with a study published in the Journal of American Medical Association earlier this month, which found that “laws that strengthen background checks and permit-to-purchase seemed to decrease firearm homicide rates.”

Everytown’s data shows that officers are safer in states with lower rates of gun ownership.

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Similarly, a study the American Journal of Public Health released last year showed that states with high rates of gun ownership had three times the number of police officer homicides as states with lower rates of gun ownership.

Shootings of police came into harsh focus this year after five officers were killed in Dallas in July, and again after two officers were ambushed and killed last month in Iowa.

While such ambush-style or seemingly at-random shootings grabbed national headlines, they “accounted for a relatively small fraction of the shootings” of police officers, according to a press release from Everytown.

Twenty-eight percent of officers shot in the line of duty this year were serving a warrant or responding to a domestic violence call ― a statistic that Everytown says “highlights the dangerous intersection of domestic violence and gun violence.” (States with expanded background checks see 46 percent fewer women murdered with guns by intimate partners, according to a previous Everytown report, and 48 percent fewer gun-related suicides.)

Everytown identified 195 of the 200 people accused of shooting police this year as men, and the sex of the other five shooters is unknown.

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A spokesman for the National Rifle Association, which opposes expanding background checks, told HuffPost it couldn’t comment on Everytown’s study without more information about how and where the data was collected.

The spokesman added, however, that Everytown’s studies usually do not control for a variety of factors that could explain a rise or fall in criminal activity. He also pointed to Oregon, which saw more shootings of police in the year after it passed a universal background check law.

Sarah Tofte, Everytown’s research director, said the group is “confident” in its research methods.

“The factors that contribute to these shootings are complicated, and no single policy can explain all of the variation,” she told HuffPost. “That said, we know from other research that background checks do save lives, and states owe it to their first responders to do everything in their power to protect them.”

Graphics by Alissa Scheller for The Huffington Post.