On average, thirty-three thousand Americans are killed by guns each year. The American Medical Association describes gun violence as a public health crisis, and a number of medical organizations and news outlets label it an epidemic. Still, the response, from a research standpoint, has been anything but comprehensive.

Here is what we do know:

Domestic gun deaths since the Robert Kennedy Assassination in 1968 outnumber deaths from all United States wars since the Revolutionary War, spanning more than two-and-a-half centuries.

Of these gun-related deaths, nearly one-third are homicides, almost two-thirds are suicide, and the remaining percentage are accidental deaths.

From a demographic standpoint, 77 percent of gun deaths in the white population are suicides while 19 percent are homicides. In the black population, this relationship is reversed, with homicides responsible for more than three-quarters of gun-related deaths, and suicides less than a quarter.

Source: CDC Injury Prevention & Control Database, Compiled by Brookings, http://www.brookings.edu/blogs/social-mobility-memos/posts/2015/12/15-guns-race-different-worlds-reeves.

Perpetrators and Victims

Racial disparities seen in the type of gun-related death also are reflected in the victims of gun violence, in both homicides and suicides. Black males are disproportionately likely to be victims of gun violence compared to their share of the population as well as to other racial and ethnic groups.

When you look at victims and perpetrators according to their mental health status, data shows that people living with mental illnesses are much more likely to be victims of gun violence, and overall violence, than perpetrators. When they are perpetrators, they also tend to be the victims, as mental illness is strongly correlated with suicide and self-inflicted harm. Still, only 3–5 percent of violent acts in the United States are committed by people suffering from serious mental health issues, and these individuals are actually up to ten times more likely to be victims of these crimes than the overall population.

This fact runs counter to the media narrative that portrays shooters as mentally unstable, which has contributed to a public misperception surrounding individuals with mental health issues and gun violence. For example a 2015 Washington Post and ABC News Poll finds that 63 percent of polled Americans believe that mass shootings are result of inadequate mental health services, rather than factors such as gun control laws.

In reality, research and experts find that components such as a history of violence, domestic violence, and substance abuse are more accurate indicators of an individual’s risk of dangerous behavior than mental illness on its own.

While this data on gun violence provides insight into the nationwide public health issue, the United States lacks more complete information. For example, the way that gun legislation such as open-carry laws impact gun violence and firearm sales, as well as the psychology behind this type of violence, are a few areas with incomplete data. This is largely attributed to a shortage of research surrounding domestic gun use and abuse.

Here’s Why We Don’t Know More

Despite the fact the federal government calls gun violence a “public health issue,” federal and private researchers have not conducted comprehensive studies on causes and prevention strategies of gun violence for two decades.

As Dr. Jay Kaplan, president of American College of Emergency Physicians (ACEP), explains, this does not line up to how the United States deals with other public health crises. Typically, once public health crises like Ebola or Zika are identified, scientific research begins so as to determine how to address them. The reaction to gun violence has been different.

“We have an epidemic of gun violence, but we are not changing procedures—at least we haven’t up to this point.”

This inaction dates back to 1996, when the National Rifle Association (NRA) accused the Centers for Disease Control and Prevention (CDC) of using the results of gun-violence research to advocate for anti-gun legislation, calling their research “propaganda.”

That year, Congress passed an appropriations bill that slashed CDC funding by the exact amount previously allocated toward firearm-related research. The law, authored by then Arkansas Representative Jay Dickey, was attached to the Fiscal Year (FY) 1997 House Omnibus Appropriations Bill and read,

“None of the funds made available for injury prevention and control at the Centers for Disease Control and Prevention may be used to advocate or promote gun control.”

This sentence began a twenty-year moratorium on federally funded gun violence research.

President Obama has worked to lift this effective ban throughout his presidency to little success. Reacting to a series of mass shootings during his first term, in January 2013, Obama issued twenty-three executive orders in an effort to promote gun safety. One directed the CDC to “conduct or sponsor research into the causes of gun violence and ways to prevent it.” While the CDC has taken steps toward conducting research, it has yet to fully comply with the executive order, and Congress has repeatedly blocked attempts to acquire additional funding. Multiple sources identify the NRA as playing a role in impeding research both through blocking funding and political intimidation. The NRA did not respond to multiple requests for comment on this piece.

Some researchers have worked around these barriers since the private sector does not face the same restrictions in administering research on the topic. Independent organizations along with nonprofits have produced some pertinent data on gun violence in recent years. For example, Harold Pollack, a Century Foundation Fellow and co-director of the University of Chicago Crime Lab, has researched where criminals obtain their guns to help guide law enforcement policies. However, as Dr. Kaplan remarks, these organizations lack the funding and organizational capacity the federal level has to make a deeper impact.

…One of the few undeniable facts that has emerged is that domestic gun-related violence is a public health issue significantly lacking research.

The American Medical Association along with a host of physician-led agencies are renewing calls for more research following the deadliest mass shooting in U.S. history that left forty-nine dead in Orlando. While the outcomes of these efforts—along with information surrounding gun violence—are unknown, one of the few undeniable facts that has emerged is that domestic gun-related violence is a public health issue significantly lacking research.

As Director of Johns Hopkins’ Center for Gun Policy and Research Daniel Webster said in an interview with The Atlantic, “I think people assume that we have a lot more information than we really do when it comes to guns, and that’s definitely not the case. We have precious little data.”

With so many lives on the line, “precious little data” may simply not be enough.