Credit default swap gives you something to do. You can buy some credit default swaps from them to protect yourself against the bankruptcy of people who owe you money.

If you have information that a company is not as good as its stock market valuation, you don't have a way to sell that stock unless you already own it. And so that information doesn't get incorporated in the company's stock price as fast if you don't allow short selling.

So what is the role that credit default swaps can play in an economy? Well my feeling is that if these things actually will now be traded on either exchanges or some kind of central clearing, they are going to be a very good measure of the credit worthiness of different companies.

There are a lot of ways that investment banking models work, but these risks are not internalized by the people that are taking them.

Allowing short selling is allowing people to sell - instead of having to buy the stock and then sell it, which doesn't do much; allow them to sell it, and then buy it. In which case they can express that information and the idea is that you would get more accurate valuation of companies by letting people express both their positive information and their negative information through either long or short selling.

We're talking about should we increase taxes? Why not put a tax on carbon emissions. It would raise a lot of money, it would reduce the environmental damages in the future, it would solve so many problems, and it would be a much more constructive thing to do than to think about raising the income tax.

I think we're fooling ourselves if we think that regulators are going to be able to outsmart the bankers. So, the task of designing regulatory reform is trying to make more or less foolproof regulation and that's one of the advantages of the systemic category.