Dow Closes Below 10K for First Time Since February

New York, NY —

The Dow Jones Industrial Average was up most of the day today, but in the last hour of trading it dropped below 10,000 for the first time since February.

The Dow has fallen about 11 percent in a month, during which time investors have been watching larger than usual swings in the stock market. Why?

Well, there's the debt crisis in Europe, a lot of speculative money moving in and out of the market at lightning speed, and then there's the very recent memory of an exploding subprime mortgage crisis that brought the U.S. banking system to its knees.

"What moves markets all the time is psychology," says Liz Ann Sonders, chief investment strategist at Charles Schwab. "It's all about psychology."

Sonders says investors haven't quite buried their angst from 2008, and that's part of the reason for the big swings in the market when scary headlines about the European debt crisis crop up.

"We know what happens when something that is perceived to be contained, i.e., subprime mortgages, turns out to be something not at all contained and very contagious in terms of the global financial system," she says.

But, Sonders says, this time is different.

American banks are not nearly as invested in European debt as they were in subprime mortgages. Which means the banks have less to worry about if countries like Greece default.

Here at home, the U.S. economy has shown broad signs of growth. And after 14 months of the Dow steadily climbing, it's not unusual to see a drop like this.

Sonders' advice to average investors: Don't try to play off these market swings. It's a dangerous game.