Tyler Cowen of the blog Marginal Revolution writes in the NYTimes about how prices carry important information and how you need trading to establish the value of securities:

To understand the depths of the current crisis, let's go back to an apparently unrelated episode in economic thought: the socialist calculation debate. Starting in the 1920s, Ludwig von Mises, the leader of the so-called Austrian School of Economics, charged that socialism was unable to engage in rational economic calculation. Without market prices, he reasoned, no one knows how much economic resources are worth.

The subsequent poor performance of planned economies bore out his point. For instance, the Soviet Union did a poor job of producing consumer goods and developing innovative industries. In the absence of well-functioning markets for capital goods, these mistakes festered, rather than being rectified by the independent judgments of individual entrepreneurs.

The irony is that the supercharged capital markets of the American economy are now -- at least temporarily -- in a somewhat comparable position. Starting in August, many asset markets lost their liquidity, as trading in many kinds of junk bonds, mortgage-backed securities and auction-rate securities has virtually vanished.

Market prices have been drained of their informational value and thus don't much reflect the "wisdom of crowds," as they would under normal circumstances. Investors are instead flocking to the safest of assets, like Treasury bills.

The absence of trading is a big problem. Financial institutions have been stuck holding illiquid assets, whose value cannot be easily determined. Who wants to lend to the institutions holding them? No wonder there is a credit crisis and a general attitude of wait and see.

This gridlock is especially harmful because leverage is so high, and financial institutions are so interconnected through swaps and loans. Institutions that rely so heavily on debt are precarious and need up-to-date information about valuations. When they don't have it, markets freeze up. This is what has taken policymakers by surprise and turned a real estate crash into a much bigger financial problem.

Read the whole thing.