So Why Did the Stock Markets Do a Bungee Jump on May 6?

What I find interesting about this story (and if you think bungee jump is hyperbole, you haven't looked at the intraday Dow chart) is there's a decent analogy: Imagine that murder victims start turning up in some small, idyllic U.S. city. Throats slashed, bodies mangled. Residents grow fearful. They start locking their doors all the time, glancing over their shoulders, going out less. The pressure mounts for police to find the killer, to calm a jittery city.

Now imagine a hit-and-run of sorts in the financial markets. Stocks make a sudden, vertiginous plunge, only to rapidly recover. Billions of dollars of wealth evaporate, then reappear. But how did this happen? Who caused it? Who profited from it? Could they do it again, and what if the next time the markets don't bounce back? And so investors grow fearful. They wonder: Should I continue to put more funds into volatile stock markets? Can they be trusted?

And the search begins, among the financial forensic teams, to find a culprit for the turbulence on May 6.

Except -- here's where our serial killer analogy breaks down -- was it really a lone actor? We'd like to think that; it fits into a more comforting narrative, with justice to be meted out if we find wrongdoing, and if we don't, we at least know where to take measures to fortify the system. Could it be Mr. Fat Finger Trader? The clumsy oaf who pressed "b" for "billion" on his keyboard when he meant "m" for "million"? Or here's the latest suspect, according to cbsnews.com:

Shares of money manager Waddell & Reed Financial Inc. fell Friday as it was identified as the stock trader that sold off a large number of index futures contracts during last Thursday's market collapse ...

Waddell's sale of 75,000 e-mini futures contracts in a 20-minute span on May 6 drew the attention of regulators, Thomson Reuters reported.

These "minis" are tied to the S&P. A futures contract is a way to bet on which way you think a market, stock or commodity is going to move; narrowly defined it's an agreement to buy or sell something at a set price on a set day in the future.

Now that 75,000 number does seem impressive. Well, at first. Wealthtrader.net tells us:

The current average daily implied volume for the E-mini is over $150 billion making it the most liquid trading derivative in the world.

What was the implied volume (I'm assuming "implied" refers to the contract's notional amount) for the 75,000-unit trade? Start with the notional value of an e-mini: $50 times the price of the S&P index. The high for the S&P that day was 2,407.8, so this trade was probably executed at somewhere south of that. Let's say the e-mini "dump" amounted to less than $9 billion of implied volume on May 6.

In other words, less than 6 percent of the typical daily volume came from this sale. Was this a big trade? Sure. Was it a little hard for the market to digest? Probably. Was it the real villain that we're seeking? I doubt it.

It's a media-ready story though. The storyline is simple. The government also surely realizes that finding a lone actor will make its job so much easier.

Unfortunately, a more sophisticated analysis of possibly the real culprit on May 6 has emerged, an analysis that is not so comforting. It suggests that our stock markets have a deep, systemic flaw. Paul Kedrosky at Infectious Greed nicely, and succinctly, laid out the argument in "The Run on the Shadow Liquidity System."

His view: good old-fashioned liquidity in the stock markets has been transformed in the age of supercomputers and high-frequency trading and algorithm-driven strategies:

... traditional providers of liquidity, market-makers and other participants, are not standing so ready to make the other side of the market. There are fewer traders prepared to make a market for the sake of market health. This is ... mostly because of what has happened with high-frequency trading, algorithms, and the like, which increasingly jump into the trading queue in front of and around orders, creating some liquidity, but also peeling pennies for themselves, frustrating market participants and heretofore liquidity providers...

The result:

... all of this changes market microstructure in insidiously destabilizing ways. For the first time we have large providers of this shadow liquidity, algorithms and high-frequency sorts, that individually account for large percentages of daily trading activity, and, at the same time, that can be turned off with a switch, or at an algorithmic whim.

Certainly we need to find what went wrong on May 6. We need to, to reassure the investing public that our stock markets are safe, fair, reliable -- places where you can feel comfortable putting a large chunk of your retirement nest egg. But, in the rush to judgment, we should be on guard against trying to largely pin the events on a lone actor, just to avoid a truth that is both complex and inconvenient.

Update: Actually, the fingerpointing at Waddell & Reed appears even more misguided than I thought ... you can blow up those calculations I made above; they were for a normal trading day. Turns out that during the 20-minute freefall on May 6, 842,514 e-mini contracts swapped hands (says Reuters). 75,000 is less than 9 percent of that number (and is probably only a few percent of the total for the day) ... again, it's sizable, but remove Waddell & Reed, and you still have a heavy, heavy volume.