Price as Information¶

Why It Matters¶

This is Hayek's fundamental insight. Central planners can't know what prices know - the distributed knowledge of millions of people making decisions. Prices coordinate without coordination. But this also means prices can be wrong when the information they aggregate is wrong.

The Key Move¶

When you see a price, ask: what information is this aggregating? Whose knowledge is reflected? A high price for a stock reflects the aggregate judgment of all traders. A rising price reflects changing information or expectations.

Classic Application¶

The efficient market hypothesis. Stock prices reflect all available information (in its strong form). You can't beat the market because the market already knows what you know. Prices are sufficient statistics for value.

Surprising Application¶

Prediction markets. Markets can aggregate dispersed information about future events. Betting odds often outperform expert forecasts because they aggregate many experts (and non-experts with local knowledge).

Failure Modes¶

Treating prices as infallible - they aggregate available information, which may be wrong
Ignoring that some information isn't reflected - private information, manipulation
Assuming all markets are equally informative - thin markets with few traders are noisy
Confusing price with value - prices reflect beliefs, which can be systematically biased
Missing reflexivity - in some markets, prices affect the underlying value they're supposed to measure

Go Deeper¶

Hayek's "The Use of Knowledge in Society." Fama on efficient markets (and the debate over its limits).

Reflexivity - Behavioral Economics: Reasoning About Systematic Deviations