Wall Street's Martingale Roulette Strategy (Backed up by the Fed)

By John Aziz


here’s nothing controversial about the claim— reported on by Slate, Bloomberg and Harvard Magazine — that in the last 20 years Wall Street has moved away from an investment-led model, to a gambling-led model.

This was exemplified by the failure of LTCM which blew up unsuccessfully making huge interest rate bets for tiny profits, or “picking up nickels in front of a streamroller”, and by Jon Corzine’s MF Global doing practically the same thing with European debt (while at the same time stealing from clients).

As Nassim Taleb described in The Black Swan this strategy — betting large amounts for small frequent profits — is extremely fragile because eventually (and probably sooner in the real world than in a model) losses will happen (and, of course, if you are betting big, losses will be big). If you are running your business on the basis of leverage, this is especially dangerous, because facing a margin call or a downgrade you may be left in a fire sale to raise collateral.

This fragile business model is in fact descended from the Martingale roulette betting system. Martingale is the perfect example of the failure of theory, because in theory, Martingale is a system of guaranteed profit, which I think is probably what makes these kinds of practices so attractive to the arbitrageurs of Wall Street (and of course Wall Street often selects for this by recruiting and promoting the most wild-eyed and risk-hungry). Martingale works by betting, and then doubling your bet until you win. This — in theory, and given enough capital — delivers a profit of your initial stake every time. Historically, the problem has been that bettors run out of capital eventually, simply because they don’t have an infinite stock (of course, thanks to Ben Bernanke, that is no longer a problem). The key feature of this system— and the attribute which many institutions have copied — is that it delivers frequent small-to-moderate profits, and occasional huge losses (when the bettor runs out of money).

The key difference between modern business models, and the traditional roulette betting system is that today the focus is on betting multiple times on a single outcome. By this method (and given enough capital) it is in theory possible to win whichever way an event goes. If things are going your way, it is possible to insure your position by betting against your initial bet, and so produce a position that profits no matter what the eventual outcome. If things are not going your way, it is possible to throw larger and larger chunks of capital into a position or counter-position again and again and again —mirroring the Martingale strategy — to try to compensate for earlier bets that have gone awry (this, of course, is so often the downfall of rogue traders like Nick Leeson and Kweku Adoboli).

This brings up a key issue: there is a second problem with the Martingale strategy in the real world beyond the obvious problem of running out of capital. You can have all the capital in the world (and thanks to the Fed, the TBTF banks now have a printing-press backstop) but if you do not have a counter-party to take your bets  (and as your bets and counter-bets get bigger and bigger it by definition becomes harder and harder to find suitable counter-parties) then you are Corzined, and you will be left sitting on top of a very large load of pain (sound familiar, Bruno Iksil?)

Read the rest here.