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Reflexivity

Why It Matters

Financial markets are reflexive. Self-fulfilling prophecies are real. Prediction and outcome aren't separable. Standard equilibrium thinking must be modified when the act of predicting changes what's predicted.

The Key Move

Ask: does believing X make X more likely to be true? If yes, the system is reflexive. A bank that's believed to be insolvent becomes insolvent as depositors flee. A stock believed to be valuable becomes valuable as investors pile in.

Classic Application

Bank runs. If depositors believe a bank will fail, they withdraw. Withdrawals cause failure. The belief was self-fulfilling. A solvent bank becomes insolvent purely through the dynamics of belief.

Surprising Application

Economic forecasting. If the central bank forecasts recession, that forecast changes behavior - businesses cut investment, consumers save more - which changes whether recession happens. The forecast interacts with its object. The economy the Fed predicts isn't the economy that will exist after the prediction.

Failure Modes

  • Treating social systems like natural systems - ignoring that participants react to models
  • Overweighting reflexivity - not everything is reflexive
  • Mistaking correlation for reflexive causation
  • Assuming reflexivity only works in one direction - negative reflexivity exists (successful prediction triggers prevention)
  • Missing that reflexivity can create multiple equilibria - beliefs can coordinate on different outcomes

Go Deeper

Soros's "Alchemy of Finance." Merton on self-fulfilling prophecies.