Washington state voters approved a ballot measure during Tuesday’s midterm elections that will significantly strengthen the state’s gun laws.

Initiative 1639 will raise the legal age to buy semiautomatic rifles — widely described as assault rifles — from 18 to 21. The measure also creates an enhanced background check, training requirements, and a waiting period of 10 business days for the purchase of such guns. And it enacts a new storage law that requires gun owners to secure their firearms, or risk criminal penalties.

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Supporters of the measure argued that it would help reduce gun violence overall, especially mass shootings.

However, research indicates that assault weapon restrictions don’t have a significant effect on overall gun violence, because these weapons are rarely used in shootings: Shootings with rifles, including assault rifles, make up less than 3 percent of gun homicides in the US.

And according to federal data from the past few decades, handguns make up the great majority — more than 70 percent — of firearms used in homicides.

Still, the restrictions might make a difference in mass shootings in particular. RAND, a policy think tank, noted in its review of the research on gun control: “Another analysis that focused on mass shooting events involving four or more fatalities between 2009 and 2016 reported that 15 of these incidents (11 percent) involved an assault weapon or high-capacity magazine, resulting in 155 percent more injuries and 47 percent more fatalities compared with other incidents.”

Restrictions on assault weapons have proven to be a popular rallying cry for gun control advocates in the aftermath of recent mass shootings, from Parkland, Florida, to Las Vegas. An assault weapons ban even has majority support, based on Pew Research Center’s surveys, not just among all Americans but among Republicans, who are generally more resistant to stronger gun laws.

So as the federal government has taken no new significant action on guns in the past few years, gun control advocates have gone down to the state level. That produced victories in Vermont and Florida this year. And on Tuesday, it led to a win in Washington state.