Financial Markets as Nonlinear Adaptive Evolutionary Systems

This paper gives an overview of joint work with Buz Brock, on evolutionary adaptive belief systems (ABS) for modelling financial markets. Recent work with Andrea Gaunersdorfer is also reviewed and some recent experimental work on expectation formation in financial markets is also discussed. Financial markets are viewed as evolutionary systems between different, competing trading strategies. Agents are boundedly rational in the sense that they tend to follow strategies that have performed well, according to realized profits or accumulated wealth, in the recent past. Simple technical trading rules may survive evolutionary competition in a heterogeneous world where prices and beliefs co-evolve over time. The evolutionary model explains stylized facts of real markets, such as fat tails and volatility clustering. Although the ABS is very simple, it is able to match the autocorrelation patterns of returns, squared returns and absolute returns of 40 years of S&P 500 data.