Counterfeiting money is the stuff of television, movies, and lore, but hardly seen by most of us – for only about one in ten thousand notes is found to be counterfeit annually.  But long ago, it was a big deal – for instance, playing a major role in the Revolutionary and Civil Wars. And nowadays, while it only directly costs Americans about $60-$80 million a year, the Treasury acts as if it is a multibillion dollar potential crime. And of course, counterfeit checks is a major crime, and source of the Nigerian schemes that pepper our email spam boxes.

My coauthor, Elena Quercioli (visiting Bocconi, soon teaching at Central Michigan), experienced the reality of counterfeiting beyond our borders in Mexico City. A merchant once informed her that a few hundred dollars worth of pesos that she had just been issued at an ATM was all counterfeit. In the USA, she would have lost the money, and been questioned by police. But there, she retained her pesos, and proceeded to find a “greater fool” upon whom to unload her losses – the crime of “uttering” (which we are told is extremely hard to prosecute even in the USA).

Elena saw that her misadventure pointed to an interesting paper on counterfeit money that might atone for her mild transgressions. The small literature on this topic never modeled the costly vigilance choice of individuals in dealing with counterfeiting. She proceeded to convince the Secret Service to give her a data trove on counterfeit dollars.  She pieced together a larger and hitherto partially unknown picture about the two flavors of counterfeit money – namely, seized money – that is confiscated from bad guys before it enters circulation – and passed money that is found at a later stage, and leads to losses by the public. Among her findings:

#1. The ratio of all counterfeit money to passed counterfeit money rises, but less than proportionately with the note.

#2. The per transaction passed rate (as a fraction of the circulation) is small for low notes, dramatically rises, and then levels off or drops. In Europe, for instance, the counterfeiting of the 500 Euro note is miniscule compared to the 200 Euro note.

(The Secret Service is under the mistaken impression that the $20 is the most counterfeit, as it fails to understand that the $50 and $100 notes circulate much less often. Go figure.)

#3. Since the 1970s, the  ratio of all counterfeit money to passed counterfeit money has drammatically fallen about 90%.

#4. The fraction of counterfeit notes found by Federal Reserve Banks falls in the note.

Cat and Mouse

I found these facts and intimations of a new theory very appealing. Our joint paper creates what may be the first multi-market “large game”, i.e. two interacting games each with a continuum of players. First, “bad guys” do battle with “good guys” in a massive game of cat and mouse. In it, good guys choose their vigilance effort  and bad guys choose their counterfeit quality – where greater quality better frustrates counterfeiting efforts. Second, since some fake money inexorably passes into circulation, a collateral game is induced, this one pitting good guys against one another. Such a hot potato game is one of “strategic complements”: Fixing the counterfeiting rate, the more carefully I expect the next guy to examine his notes, the more carefully I must. We show that this second market fixes the counterfeiting rate.

The whole exercise has proved an exploration of nanoeconomics – for instance, we can deduce that individuals expend at most ¼ a cent of vigilance attention looking at the $100 note, and much less for lesser notes. I must say that the paper has reinforced my faith in economics. For despite such miniscule attention costs, the theory does a decent job of simultaneously explaining all the above patterns in counterfeiting – for instance, even the nonmonotone one emerges, that the passed rate rises and then falls. We even do a darn good job absolving the Secret Service of any incompetence in the plummeting seizure rates.