Immediate theories:
- It was the computers, stupid. This seems likely to have been at least part of the problem; the drop was just too sudden, as was the recovery. Accenture dropped from $40 a share to one cent at some point, and Proctor and Gamble also had an improbably gigantic drop. I’d guess that some trading programs, somewhere, hit the wrong stock price level and went horribly wrong.
- The market knows something that we don’t about Germany. Now that Greece has passed its austerity plan, the rest of the eurozone has to go along. Germany, the single biggest player, votes tomorrow, and maybe someone knows we’re headed for a nasty surprise.
- The market knows something that we don’t, but ought to, about Greece. Greek approval of the austerity plan should have perked things up. Instead, the markets are in turmoil. And maybe they’re right to be. Passing an austerity plan doesn’t guarantee that it will work; Argentina was going through governments like paper plates right before it terminated the dollar peg and defaulted.
- The market doesn’t know anything we don’t, but some idiots panicked when Mohamed El-Erian said that Greek contagion was on the verge of spreading. One of the more comforting explanations; if so, the idiots seem to have thought the better of it.
- Someone unwinding a giant euro-yen trade touched off some sort of temporary panic as people fled risky assets. That’s au courant on Bloomberg. Somewhat comforting–but not very, because if the markets are this vulnerable to panic, there’s an underlying anxiety that may blossom into something worse.
- Some hedge or bond fund manager is manipulating the market for personal gain. Maybe. But a collapse this broad across multiple asset classes is pretty hard to orchestrate, so not very likely.
Update: Via Twitter, NASDAQ seems to be confirming that at least part of the problem was a faulty Proctor andd Gamble quote.
