I’ve been looking into violent deaths lately. And now I understand a few things. Mostly, I understand what we don’t know about violent death in the United States. For instance, consider one of the most horrific kinds of violent death — mass shootings in public places like malls and offices and schools.

How often does this happen somewhere in the United States?

Nobody knows.

What kind of people wield the guns involved? How old are they? Do they have a criminal record or a history of mental illness?

Nobody knows.

How many murders involve assault weapons? How many are drug-related?

Nobody knows.

How many teens are drunk or stoned when they commit suicide? How often does a child die from abuse somewhere in this country? How many women who die from domestic violence have a restraining order against their attacker?

Nobody knows.

I thought the answers to these questions would be easy to find. How wrong I was.

What I found was some information from a few states, but nothing systematic. Nothing that reports national-level data on violent death, which includes murder, suicide, domestic violence, and child abuse.

And I found a system that could provide this information. The National Violent Death Reporting System gathers data for every violent death from a variety of sources. By getting records from the police, medical examiners, crime labs, hospitals, and public health officials, the NVDRS can paint a picture of how and why people die the kind of deaths that spawn nightmares and media storms.

The NVDRS currently operates in 17 states. That’s all the funding there is. Housed at the Centers for Disease Control and Prevention, it depends on federal funding. It’s relatively inexpensive, too. Another $4 million for FY2009 would expand participation to more than half the states, so email your Congressional delegates.

Why should you bother? This isn’t just about having numbers. It’s about keeping people from becoming victims. Trying to prevent violent deaths without data about the how and why of it is like trying to treat cancer based on a biopsy report that’s missing most of the words. You might guess right, but the odds are against you.

And if you’re wrong, somebody dies.