Robert Litan, director of economic studies, Brookings Institute

The World Trade Center is the home of American Express and Merrill Lynch. Morgan Stanley had a huge presence there, and Lehman Brothers is there. You have a bunch of other financial institutions there, including a number of foreign banks.

The only reason that I raise all this -- apart from the terrible tragedy to the people at those companies -- is that these are huge firms; they all have counterparts that they owe money to. When the markets open people are going to be calling and e-mailing to get their money. They're on the other sides of trades, whether it's derivatives or stock orders. They engage in billion and billions of dollars of financial transactions where they are supposed to ship money to people and people are supposed to ship money to them. The people that they owe money to are going to be worried about how they're going to get paid.

One assumes that they've got computer backup facilities. But if you're a counterpart to someone at American Express or Merrill Lynch or wherever, you may need a loan and you [don't] know whether or not you're going to get paid.

I'd have to say that it's worse than it appears.