Many basic questions remain largely unanswered as a result. It’s difficult, for example, to pin down the precise impact of specific gun laws—like laws that allow people to openly carry firearms. Do open-carry laws make gun violence worse, or do they cut down on firearm injuries and deaths? Researchers can’t say with certainty. They also don’t know much about the path that guns take in order to fall into the hands of criminals, or how gun laws impact firearm sales on the black market. For that matter, the psychology of gun violence is not well understood. What motivates people to use guns to commit a crime or suicide, and what are the most effective ways to stop mass shootings, gun-related homicide, and suicide? Limited research makes it challenging to reach well-supported conclusions.

“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,” said Daniel Webster, the director of Johns Hopkins’s Center for Gun Policy and Research. “We have precious little data.”

Of course, gun violence is not the only area of research where politics and science clash. Climate change is a contentious subject that proves evidence doesn’t eliminate controversy. In the case of climate change, research has yielded a scientific consensus that man-made global warming is a real threat. But that hasn’t stopped a political debate over the existence of climate change from raging on Capitol Hill. Still, the ability to cite that consensus helps frame the debate, making it possible for the media, and anyone else, to more easily discredit the arguments of politicians who deny the science. Data acts as a check on rhetoric that has become untethered from reality, and evidence informs the creation of effective policy to deal with the threat.

In contrast, a scarcity of statistics on gun violence allows the political debate over gun control to take place in a realm that is often largely separate from actual fact. A lack of research makes it difficult to know which laws and regulations would reduce injuries or deaths from firearms and under what circumstances they might do so. When it comes to talking about gun laws, politicians are, to some extent, operating in the dark. “It’s very concerning that there’s been an attack on science and the ability to carry that out,” said Fred Rivara, a professor at the University of Washington who helped conduct a study on guns in the home in the early 1990s. “It’s resulted in a sort of stalemate in terms of being able to develop effective policy.”

To be clear, it’s not that there isn’t any research. Private foundations have stepped up to try and fill the void of federal gun-violence research. After the Sandy Hook Elementary School shooting in 2012, President Obama called for the CDC to conduct research on the causes of gun violence and how to prevent it. But Congress was unmoved and continued to withhold funding. Still, there are some signs that government agencies are daring to defy political pressure from lawmakers and the gun lobby. A year after Sandy Hook, for example, the National Institutes of Health put out a call for research on firearm violence in a direct response to the president’s plea.