Admit it, you were hoping that Monday's 416 point plunge in the Dow was a one-shot deal and that yesterday's market was the beginning of a recovery. This morning an e-mailer suggested that "Perhaps you should wait for educated or experienced opinions before you issue your comments."

I'm sure of one thing. I can't explain why stocks go up or down. But this morning the market is continuing the plunge that began in Shanghai a few days ago and spread around the world. Some of my esteemed colleagues here have put together lists of "bargain stocks." But are they bargains if they keep going down?

Here are some reasons that I've cited in previous posts for this morning's market decline:

• Reversing the Yen Carry Trade. This morning's Wall Street Journal [subscription required for all WSJ links] alludes to the role that this trade -- in which investors buy cheap Yen to invest in higher yielding investments -- is reversing due to a strengthening Yen. Hedge funds have been borrowing money to finance the Yen and when their trades go against them, they desperately sell their other holdings to come up with the cash needed to repay the Yen loan.
• Subprime mortgages bleeding into the rest of the economy. Again the WSJ writes about this phenomenon this morning. It notes that defaults are starting to spread to the $400 billion "Alt-A" mortgage category which is supposedly less risky than subprime. The bleeding has not yet spread across the global economy but it seems to be moving there.
• Geopolitical instability. It's not really clear whether North Korea will get rid of its nuclear weapons or whether Iran will use them. Meanwhile, the U.S. is positioning military assets near Iran.
• Growing risk aversion. The WSJ also suggests that investors' appetite for risk has been satisfied and therefore risk premiums will climb and cut off the flow of debt to fuel rising asset prices.

As I noted in earlier posts, the key is to remain calm and take a five to 10 year view if you can afford to do so.

Peter Cohan is President of Peter S. Cohan & Associates, a management consulting and venture capital firm. He also teaches management at Babson College and edits The Cohan Letter.