Human Dynamics in Markets (Nonlinear Systems)

“From Efficient Markets Theory to Behavioral Finance”
Robert J. Shiller
The Journal of Economic Perspectives
Vol. 17, No. 1 (Winter, 2003), pp. 83-104 (22 pages)
Published by: American Economic Association

On page 86, Figure 1, the real price of S&P 500 is wiggly, which visually llustrates volatility. The other lines in the graph are smooth, representing expected values for a rational market.
Behavioral Finance: https://en.wikipedia.org/wiki/Robert_J._Shiller