This post by Jason Alexander on public ownership of firearms has been making the rounds on my Twitter feed lately, and I need to interject some facts into the discussion.

Despite these massacres recurring and despite the 100,000 Americans that die every year due to domestic gun violence - these people see no value to even considering some kind of control as to what kinds of weapons are put in civilian hands.

This number is off by a factor of 3-10, depending on what you mean. The total number of gun deaths in the US is roughly 31,000 per annum. The US is the country with the highest incidence of gun deaths per capita, which probably has something to do with a quarter of US citizens and roughly half of households owning guns.

The distribution of gun deaths is bimodal: most are suicides, which are most prevalent among old white males, especially those in rural areas, the south, and veterans. Reflect for a second: this is how many of us choose to die.

The other big chunk of gun deaths is homicides, of which there are ~11,000/year, decreasing over the last decade. Their victims tend to be 10-24 years old (tapering with age) male, poor, and African American, Native American, or Hispanic. How much of that race effect is actually SES I don’t know, but I’d bet on it being a significant factor.

Accidents and justifiable homicides (e.g. law enforcement actions, citizens defending themselves) are relatively infrequent by comparison.

Lastly, there are these well-intended realists that say that people like this evil animal would get these weapons even if we regulated them. And they may be right. But he wouldn't have strolled down the road to Kmart and picked them up. Regulated, he would have had to go to illegal sources - sources that could possibly be traced, watched, overseen. Or he would have to go deeper online and those transactions could be monitored. "Hm, some guy in Aurora is buying guns, tons of ammo and kevlar - plus bomb-making ingredients and tear gas. Maybe we should check that out."

KMart isn’t cited in any news article I can find. The NYT states that Holmes ordered his ammunition, gear, and magazine online. The guns were purchased legally from Gander Mountain Guns and Bass Pro Shops, both of which fulfilled their background check requirements. Not that it mattered, because this guy had no criminal record, just speeding tickets. That right there should suggest a problem with making general policy arguments on the basis of the Aurora case: violent crime is strongly predicted by prior conviction for felonies or violent misdemeanor. This is an exceptional case: targeted measures to prevent similar incidents will necessarily be exceptional, e.g., not applicable to the majority of violent crime.

Untargeted measures, like banning all private gun ownership, would probably work well. I support this idea from a public health standpoint, though it’s politically untenable.

Regulated, he would have had to go to illegal sources - sources that could possibly be traced, watched, overseen.

Illegal channels are easier to regulate. Riiiiight.

It’s more complicated than you might assume. Most ATF trafficking investigations identify straw purchasers as the primary source of guns for young offenders. Theft is another important source. Many guns are given or sold privately, which is difficult to regulate and track, especially on a predictive time frame.

[assault rifles] are the weapons that maniacs acquire to wreak murder and mayhem on innocents. They are not the same as handguns to help homeowners protect themselves from intruders.

They are different. Of US weapon-categorized firearm homicides, only ~5% were caused by rifles of any kind. Handguns, on the other hand, were associated with 76% of deaths.

This probably has something to do with the fact that violent criminals consistently state a preference for concealable, high-quality, large-caliber, high-capacity handguns. Handguns are most frequently used in crime, make up the majority of stolen guns, and are involved in the bulk of law enforcement officer deaths. Juvenile offenders do frequently report possessing military-type weapons, but fewer than 1% say they carried the weapon at the time of their incarceration.

I'll say it plainly - if someone wants these weapons, they intend to use them.

Data about assault rifles is hard to come by. Rifles are incredibly prevalent (and are much less likely to be used in crime), but the majority of them are intended for hunting. I’ve seen (but can’t cite an accurate source) a figure of 4 million “assault rifles” extant in the US, which lets us place an upper bound on the probability an assault rifle will be involved in a homicide: (438 rifle homicides + 1354 uncategorized weapon homicides) * 20 year lifespan / 4,000,000 assault rifles ~= 0.006. I don’t buy it.

We had an assault rifle sales ban in the US, but the CDC and independent researchers were unable to establish its effectiveness. In fact, the CDC’s literature review found mixed or null support for basically all gun control laws. Why is it so hard to establish effectiveness? Lack of controls, lack of good categorization data for violent outcomes, underreporting of non-homicide crime, and decade-scale time dependence in US violence. Luckily, data collection is improving, which gives me hope that we’ll find stronger evidence for targeted social and technological intervention in the future.

That’s not to say that sales controls are useless, just that it’s a hard problem. I particularly like the methods and discussion in Wintemute, Wright, Drake, & Beaumont 2001, examining California’s 1991 law preventing the sale of handguns to violent misdemeanants. They found a relative risk reduction of ~20-25% among that population, and have some interesting comments on regulatory intervention in general.

WHY DO YOU NOT, AT LEAST, AGREE TO SIT WITH REASONABLE PEOPLE FROM BOTH SIDES AND ASK HARD QUESTIONS AND LOOK AT HARD STATISTICS

Indeed. The problem is that we, as humans, are really bad at statistics. Removing every assault rifle from existence could only prevent (if the FBI categorization data is representative) five percent of US homicides, and that’s assuming those murderers don’t just switch to other guns. But because the story of a theater shooting is unusual, tragic, and compelling, we focus on this particular class of scary weapon. Even though preventing rare events by unstable, motivated individuals is incredibly difficult, we forgo examining the larger, systemic problem: it isn’t present, isn’t compelling. We ignore automobile deaths but freak out over terrorist bombings. Both are tragedies, but only one’s a story.

I’ll let you guess which kind of violence we’re better at preventing.

You may also be interested in Robert Brown's response, which dives deeper into weapon types and suggests a national monitoring scheme.