An employee of North Raleigh Guns demonstrates how a “bump stock” works at the Raleigh, N.C., shop. (2013 photo by Allen Breed/Associated Press)

In 1996, the Centers for Disease Control and Prevention ceased funding gun violence research as a result of the National Rifle Association-backed Dickey Amendment, which prohibits the agency from using federal funds in ways that could be construed to “advocate or promote gun control.”

The chilling effects of that amendment, which has been reauthorized by Congress every year since then, are laid bare in a pair of charts published earlier this year by the Journal of the American Medical Association. For starters, here's a look at the mortality rate for the top 30 causes of death in the United States vs. the amount of federal dollars available to do research into those causes.

Gun violence stands out because it has a relatively high mortality rate, coupled with rock-bottom federal funding compared with other, equally deadly conditions such as sepsis, liver disease and motor vehicle accidents.

“Gun violence killed about as many individuals as sepsis,” authors David Stark and Nigam Shah note. “However, funding for gun violence research was about 0.7 percent of that for sepsis.” Not 70 percent, not 7 percent — 0.7 percent.

That lack of funding translates directly into less research being done on how to prevent or mitigate gun violence. Here's Stark and Shah's second chart, showing the volume of papers published for each of the 30 causes of death.

Again, gun violence stands well apart from most of the others. As noted above, gun violence kills about as many people each year as liver disease. Between 2004 and 2015, there were more than 100,000 papers published on the latter topic and just over 1,000 published on the former.

“In relation to mortality rates, gun violence research was the least-researched cause of death and the second-least funded cause of death after falls,” Stark and Shah write.

This represents a huge blind spot from a policy standpoint. You can't reduce gun injuries and deaths if you don't know which policy changes will make a difference. While some research has nonetheless proceeded over the past 20 years, our knowledge of the issue is woefully incomplete relative to what it could have been had Congress allowed federal gun research to continue unimpeded.

It's no coincidence Congress has done little on guns in the past 20 years, even as the gun policy landscape, from technical advancements to the rise of mass shootings, has evolved rapidly over the same time period.