Hundreds of Gun Control Bills Have Been Introduced Since Sandy Hook. Why Has Nothing Changed?

As communities mourn the 31 lives lost in two separate mass shootings earlier this month, Congress is once again struggling to offer comprehensive gun control laws in place of thoughts and prayers.

The attacks in El Paso, Texas, and Dayton, Ohio—occurring within 24 hours of one another—brought the national count of mass shootings to 19 this year alone, according to the AP/USA Today/Northeastern University mass murder database. Politicians have renewed calls for the implementation of broader background checks and condemnation of President Donald Trump’s anti-immigrant rhetoric, which likely contributed to the El Paso shooter‘s motivation.

It’s a familiar cycle. The United States has long had a problem with gun control: The mass murder database states there have been at least 18 mass shootings every year since 2006, accounting for more than 1,700 deaths altogether. After each major tragedy, Congress attempted to pass legislation to prevent the next one.

When a gunman opened fire on Sandy Hook Elementary in December 2012, killing 20 children and six adults, the nation was appalled. The House and the Senate each passed resolutions condemning the violence, and in the following month and a half, at least 22 gun-related bills were introduced. None passed.

Since then, there have been more than 550 gun-related bills and joint resolutions introduced in Congress. Of the handful that have become law, none implemented new restrictions on gun ownership.

Where Congress has failed, states have made some progress. Federal law does not require gun owners or buyers to have a license, but 14 states and Washington, D.C., have some sort of licensing program, according to the Giffords Law Center. Federal law only requires a gun buyer to undergo a background check if the weapon is purchased through a licensed dealer, meaning private sales go unregulated, but 21 states and Washington, D.C., have extended the background check requirement to include at least some private sales.

Similar legislation has been introduced at the federal level over the years, but no bills have been passed.

“It’s been a little bit frustrating because for years we’ve seen broad public support for many of these policies,” Dr. Cassandra Crifasi, deputy director of the Johns Hopkins Center for Gun Policy and Research, told Fortune.

A 2017 poll by the center found “large majorities of both gun owners and non-gun owners strongly support measures to strengthen U.S. gun laws,” yet hundreds of bills have been held up in committee review or placed on the legislative calendar and then neglected.

“I think many of our elected officials have not felt like they needed to be accountable to constituents promoting evidence-based policy changes to prevent gun violence,” said Crifasi. “There’s a disincentive to bring these policies up for a vote, because it’s one thing to talk about policy… but it’s a different thing to actually have your name associated with a vote.”

Senate Majority Leader Mitch McConnell, for example, has avoided putting to vote two House bills on expanded background checks. The House passed the bills in February, but McConnell placed them on the Senate legislative calendar to be addressed at a later date.

The public, however, is tired of waiting for action. Whereas mass shootings typically create an uproar and then fall from the media within a week or so, said Crifasi, the student survivors of the shooting at Marjory Stoneman Douglas High School in Parkland, Fla., have refused to step out of the national spotlight.

“They have not let this fall out of public discourse the way that other incidents of mass shootings have,” said Crifasi. “They mobilized and organized folks and are getting voters registered. They’re taking specific action to stay engaged in the conversation in a way that didn’t necessarily happen before.”

Moreover, gun safety advocates around the country are taking to the polls as single-issue voters, said Crifasi, countering the decades of voters on the flip side that have historically voted solely in favor of nonrestrictive gun laws.

“I don’t know that that’s going to translate into movement at the federal level, but I do think that there’s a growing frustration in the U.S. public,” said Crifasi. “That may translate into folks showing up at the ballot box in November and perhaps electing themselves some new policy makers.”

If and when Congress takes action, it’ll come in the form of several different pieces of legislation, said Crifasi. “Gun violence doesn’t have just one policy solution,” she said. “There are different policies that are going to be needed to prevent these different forms of gun violence.”

Lawmakers have already proposed hundreds of bills addressing different aspects of gun control—magazine sales, background checks, research funding, and more—it’s just that none have passed.

“We have them,” Crifasi said. “We just need our legislators to step up and call them to a vote.”