Credit card activity as a predictor of mass shootings

The New York Times has published an investigation into infamous American mass shootings and found that a significant proportion of mass shooters go on credit-card fueled spending sprees prior to their acts of terror, and that these shooters worry (needlessly, as it turns out) that their unusual credit-card spending will be flagged by financial institutions, resulting in their cards being frozen.

Even if you don't own one or more guns, the historic, incredible wealth of the NRA tells you something about the profitability of the industry -- and hence the high price of the bulk-killing weapons that mass-murderers prefer.

This presents a problem for law-abiding hoarders of high-powered, high-speed, high-capacity firearms, who may lack the funds to amass the arsenal of their dreams. But mass killers, who plan on dying in a hail of bullets after they have done their work, can sidestep this problem thanks to the American dream of easy subprime credit, as the high interest rates and fees associated with the cards you can get on short notice pose no hardship to the intestate estates of notorious killers.

Anyone who's ever used their cards in unusual ways knows all about the hair-trigger fraud-detection systems used by banks: I can say from recent experience that even if you call your bank and tell them, "I'm about to do all my annual charitable giving, so please expect a bunch of unusual transactions ranging from $100 to $3000, all to registered charities," that you will still have to call the fraud department and get your card unfrozen half a dozen times. And don't get me started on the risks of having your card frozen while you're out of the country -- even if you warn your bank ahead of time -- with a dead phone battery and no way to call overseas to ask your bank to unfreeze things.

But somehow, mass shooters don't get caught in this dragnet. In part, that's due to a deliberate strategy of obscurity pursued by gun merchants, who piggyback on the Merchant Category Code for sports stores, and who supply only the minimum information required to process the transaction, not volunteering the fact that their customers are buying assault rifles and other killers' friends.

The Times's investigation ends by suggesting that banks are unwittingly complicit in mass shootings, and that they could do better: increasing both the data they demand from merchants and the sensitivity of the fraud-detection systems that interdict suspicious transactions. Andrew Ross Sorkin cites the role that banks have been deputized to play in fighting the financing of terrorism and money-laundering as predecent.

As someone who is pro-gun-control and anti-bank, I should be cheering this on, but I think it's a terrible idea.

First of all, mass shootings are incredibly rare (not relative to other countries, but as a cause of mortality -- you are almost certainly not going to get caught in one, but you should be much more worried about being shot deliberately or accidentally by someone you love, or about killing yourself with your own gun, all of which constitute the bulk of the risk from guns in the USA).

If, say, one in a million high-dollar transactions at a place where guns are sold is a prelude to a mass killing, and your mass-killing-detector algorithm is 99% accurate then:

* Out of every million transactions, 10,000 will be flagged as potential mass shooters

* Out of every million transactions, only one will be an actual mass shooter

* For every 10,000 leads that the banks pass on to police, 9,999 will be false alarms

This is not a good way to fight crime.

What's more, Sorkin's math contains a glaring flaw: while he correctly identifies that spending a lot on credit cards is a good predictor of mass shootings, he doesn't ask whether it's a good predictor of things that aren't mass shootings. This is really important, because if, say, outfitting a big hunting trip, or adding to a collaction of rare and expensive firearms, are thousands of times more likely than tooling up for a mass killing, then the rate at which false alarms are sent to the cops will be much higher than the math above suggests.

Then there's the precedents that Sorkin cites as the basis for asking banks to fight this kind of crime: their efficacy in fighting money-laundering and terrorism. The problem is, banks suck at this. The anti-money-laundering measures put in place have done little to deter the worst money-launderers (see, e.g., the Panama Papers), while they have put incredible hardship on some of the most vulnerable people in our world -- like, say, undocumented immigrants making remittances to their families overseas. Even people with loads of privilege and relative wealth suffer from this (I remember when Citibank UK refused to let me withdraw a thousands pounds in cash on my wedding day, which I wanted to have on hand in case there were problems with the caterer, the hall, etc, that could be resolved with cash money).

Sorkin's committing elementary logic errors here: just because a certain credit-card spending pattern predicts gun violence, it doesn't follow that gun violence is the thing is predicts best, nor that we could detect it well -- and if the best evidence for banks as crimefighters is the money-laundering and terrorism-fighting they do, then we should ask ourselves whether they're very good at doing either, and what costs this imposes on people who aren't money-launderers or terrorists.

Walmart and Dick's Sporting Goods this year announced that they would not sell firearms to anyone under 21. If banks chose to use the systems they already have in place, they might decide to monitor such customers, perhaps preventing them from buying multiple guns in a short period of time.

"They can fine-tune their own systems, because in these cases the suspicious purchasing patterns could have been picked up on and quite frankly should have been picked up on," said Mr. Sullivan, the Anti-Money Laundering Training Academy president.

Banks could also add information about gun sales to the infrastructure they already use to help the government investigate other criminal activity.

"We need to step back and think about what tools we use to combat terrorism and money-laundering and think about the financial rules associated with the Patriot Act," said John Streur, chief executive of Calvert Investments, a mutual fund firm that is an advocate for responsible investing. "In a very real sense, I think these mass shootings are terrorism."

How Banks Unwittingly Finance Mass Shootings [Andrew Ross Sorkin/New York Times]