The most awkward flash-crash possible

When your stock exchange wipes 99.75 per cent off its own value in less than a second, it might be t

London 2004, back when trades were done by people, not Skynet. Credit: Getty

Felix Salmon shows us his chart of the day, from Zerohedge (click for big):

He explains:

What you’re seeing here is the price of shares in BATS, at 11:14 [Friday] morning [ET]. The white spots are trades: there are 176 of them altogether. They start just below the IPO price of $16, and then just fall lower and lower and lower until the stock is trading for mere pennies. But the key number you want to look at here is not on the y-axis. Instead, it’s the chart report at the very top:

Elapsed Time: 900 Milliseconds

BATS, which stands for Better Alternative Trading System (a name which will surely come to haunt them), is a stock exchange based in Kansas. While most American stocks are listed in one of the two big exchanges, NYSE or Nasdaq, there are multiple venues where stocks can be traded – around 50. These exchanges communicate with each other to work out a "national best bid/offer" (NBBO), which is kept consistent throughout the venues. At least, that's the plan.

What appears to have happened is that a "software bug" (BATS aren't particularly forthcoming with the details) severed, or otherwise corrupted, the link between BATS and the NBBO system for all stocks beginning with A or B. This combined with the high-frequency trading that operates heavily in BATS (indeed, which it was largely set-up to enable) to allow stocks to plummet in less than a second.

For the most part, no-one was hurt. The error was confined to the one exchange, which rolled back the transactions. We would have all learned a valuable lesson about the dangers of computer-aided trading, the proponents of a financial transactions tax would have another weapon in their armoury (high-frequency trading isn't financially viable with a financial transactions tax in place), and everything would go back to normal. We would have, were it not for an excruciating coincedence:

The share that is charted above is that of BATS itself - that is, the company running the stock exchange which suffered the glitch. Not only that, it is the value of BATS on the day it held its initial public offering. Awkward.

BATS the company was supposed to be the first one to be listed (as opposed to merely exchanged) on BATS the exchange. For a smallish company based in a suburb of Kansas City, that is quite a big power grab. Needless to say, it didn't go to plan. The IPO is now cancelled, and the company has "no plans" to try it again soon. Which is unsurprising.