There were basically four questions that we were trying to answer. The first question is what is the problem? Who were the victims? Who was killed? Who were injured? Where did they happen? Under what circumstances? When? What times of the year? What times of the day? What was the relationship to other events? How did they happen? What were the weapons that were used? What was the relationship between the people involved? What was the motive or the setting in which they happened? The second question is what are the causes? What are the things that increase one's risk of being shot? What are the things that decrease one's risk of being shot? The third question we were trying to answer is what works to prevent these? What kinds of policies, what kinds of interventions, what kinds of police practices or medical practices or education and school practices actually might prevent some of these shootings? We're not just looking at mass shootings, but also looking at the bulk of the homicides that occur every year and the suicides, which account for a majority of all gun deaths. Then the last question is how do you do it? Once you have a program or policy that has been proven to work in one place, how do you spread it? How do you actually put it in place?

Before the NRA got its way, the CDC had already learned, 20 years ago, that having a gun in the house meant that someone living there was 300 percent more likely to die of a firearm homicide than someone living in a house where no guns are kept. That, in fact, was the study that irked the NRA into action.

Rosenberg's team was also looking into the who, what, where, when and how of shooting incidents under the Firearm Injury Surveillance System.

Key questions today, he said, are exactly what you want from a scientific study: What are the positive and negative effects or likely to be the effects of certain policies based on the data? Are assault weapons bans effective? Limits on the capacity of gun magazines? What about registration and licensing?

It's not up to the CDC to decide whether to pass measures it thinks might work. Those are political decisions for us and our elected representatives to decide.

But how in hell are we and they supposed to make intelligent choices if they are constrained by a lack of good, independently collected information? The NRA wants our representatives, and the American people, to be kept in the dark. Or supplied with information about guns that is no more verifiable than the membership of four million that the organization claims.

What laws, if any, should be passed to reduce gun violence is a moral question, a political question, a constitutional question. That makes it a matter of argument among people with very different points of view.

But we should all be able to agree that self-interested parties in this debate should not be allowed to continue blocking the gathering and interpreting of scientific data on the subject. Ignorance never leads to good outcomes. The NRA has done its best to keep us ignorant for a long time.

