In the wake of yet another mass shooting tragedy today, let’s examine the costs and benefits of high capacity gun magazines. I previously examined the cost-benefit of private gun ownership in the US, and noted at that time that the extraordinarily negative cost-benefit ratio might eventually become an issue for the pro-gun lobby (the industry generates economy-wide economic losses of over $15B/year) .
High capacity magazines  seem to have become a feature of virtually every recent mass-shooting in the US . How many lives might have been saved by eliminating high-capacity magazines? Let us conservatively assume 10 deaths per year might be reduced through this policy (a rounding error compared to the roughly 10,000 annual gun homicides in the US). The economic value of 10 lives can be estimated at $80 million, while the annual sales revenue of high-capacity magazines might be less than $20 million (since gun magazine sales are a tiny fraction of gun sales, and magazines can be had for as little as $15) .
Measuring tragedy on an economic basis might seem crass, but it helps establish a key point: not only are high capacity magazines empowering individuals in mass shootings – but they are also provably hurting America as a whole, as they subtract value from our nation! An outright ban on possession of high capacity magazines is thus a reasonable step to limit further damage to America’s citizens and economy.
Let me address a number of potential criticisms here:
- Would-be mass shooters will acquire weapons and high-capacity magazines illegally, so you are only affecting law abiding citizens. Actually, 75% of weapons used in mass shootings were acquired legally, and recent shooters acquired their weapons legally. Most of these shooters had no previous criminal record, so in the event high-capacity magazines were illegal, it’s unlikely that they would even know how to find them illegally.
- Banning high-capacity magazines would have no effect on death rates, as shooters would simply reload. In the Gabrielle Giffords shooting, the gunman was stopped in his rampage once he stopped to reload. Reducing magazine capacity to 10 rounds reduces total firing capacity – this is simple arithmetic. In both of these shootings and many other incidents, lives would have been saved. For that matter, lives might be saved in incidents like drive-by shootings where the rapid fire of multiple rounds makes victims of innocent bystanders.
- High capacity magazines are needed for self-defense. Even the police rarely find need to fire large numbers of rounds. Is there even one documented case of self defense where the potential victim needed more than 10 rounds to deter his attackers? There are outliers in everything, but I’d be surprised to hear of such a case.
- I have a 2nd-Amendment right to whatever capacity magazine I like. The recent Supreme Court case upholding an individual right to a firearm also upheld the right to ban American citizens’ access to fully automatic weapons, grenades, tanks, and all other manner of military weapons. Even Justice Scalia admits that there are restrictions on the 2nd Amendment. Your right to purchase whatever weapon you like has long since been curtailed, and the government retains the right to enact reasonable restrictions on access to arms.
 Using more recent numbers on the economic value of human life at $8M per life, the gun industry may actually cause annual economic losses in the US of $200B per year (8M * 30k lives lost – economic value of gun trade). I republished the more conservative estimate above to remain consistent with the original analysis that I referenced.
 I am defining high-capacity magazines as those holding more than 10 rounds, as defined in the original assault weapons ban.
 Limiting gun capacity would have reduced casualties in a number of recent tragedies:
- Today’s CT school shooting – the shooter used both Glock and Sig Sauer handguns. Glock handguns typically hold 17+ rounds, and so are always capable of discharging a high number of rounds before reloading.
- Gabrielle Giffords shooting – Jared Loughner used a 33-round magazine with his Glock handgun.
- Virginia Tech – Multiple Glock handguns were used in this and many other mass shootings.
- Columbine, CO – The perpetrators were armed with a TEC-9 with multiple high-capacity magazines, among other weapons.
- Aurora, CO – James Holmes used multiple weapons, one of which had a 100 round magazine, and produced a steady stream of fire rendering it difficult for victims to escape.
- If you’re still reading this list, and can’t comprehend the simple arithmetic involved – that greater firing capacity leads to greater damage in mass shootings – then you are willfully ignorant.
 Gun sales are estimated to have reached an annual rate around 12 million this year. If separate high-capacity magazine sales are in the neighborhood of 10% of all gun sales, and magazines cost around $15, then total annual revenue from this business might be 1.2M * 15 = $18M. This is an imprecise estimate, since gun sales are not tracked, but conveys the order of magnitude, and illustrates the tiny economic benefit supplied by this particular product relative to its cost in human life.