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

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.

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

Alex Hern is a technology reporter for the Guardian. He was formerly staff writer at the New Statesman. You should follow Alex on Twitter.

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How Theresa May laid a trap for herself on the immigration target

When Home Secretary, she insisted on keeping foreign students in the figures – causing a headache for herself today.

When Home Secretary, Theresa May insisted that foreign students should continue to be counted in the overall immigration figures. Some cabinet colleagues, including then Business Secretary Vince Cable and Chancellor George Osborne wanted to reverse this. It was economically illiterate. Current ministers, like the Foreign Secretary Boris Johnson, Chancellor Philip Hammond and Home Secretary Amber Rudd, also want foreign students exempted from the total.

David Cameron’s government aimed to cut immigration figures – including overseas students in that aim meant trying to limit one of the UK’s crucial financial resources. They are worth £25bn to the UK economy, and their fees make up 14 per cent of total university income. And the impact is not just financial – welcoming foreign students is diplomatically and culturally key to Britain’s reputation and its relationship with the rest of the world too. Even more important now Brexit is on its way.

But they stayed in the figures – a situation that, along with counterproductive visa restrictions also introduced by May’s old department, put a lot of foreign students off studying here. For example, there has been a 44 per cent decrease in the number of Indian students coming to Britain to study in the last five years.

Now May’s stubbornness on the migration figures appears to have caught up with her. The Times has revealed that the Prime Minister is ready to “soften her longstanding opposition to taking foreign students out of immigration totals”. It reports that she will offer to change the way the numbers are calculated.

Why the u-turn? No 10 says the concession is to ensure the Higher and Research Bill, key university legislation, can pass due to a Lords amendment urging the government not to count students as “long-term migrants” for “public policy purposes”.

But it will also be a factor in May’s manifesto pledge (and continuation of Cameron’s promise) to cut immigration to the “tens of thousands”. Until today, ministers had been unclear about whether this would be in the manifesto.

Now her u-turn on student figures is being seized upon by opposition parties as “massaging” the migration figures to meet her target. An accusation for which May only has herself, and her steadfast politicising of immigration, to blame.

Anoosh Chakelian is senior writer at the New Statesman.

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