According to Standard & Poor's data, total annualized return of stocks from 1926 through 2013 was 9.9%. With the potential for those returns, however, comes greater risk. Despite all the expert advice you'll no doubt come across when researching specific stocks, there are no guarantees as to how a stock will perform; the broader market is impacted by so many forces that are uncontrollable and unpredictable -- including consumer emotion, political events, and natural disasters. That said, long-term historical market performance data demonstrates the potential benefit of investing in stocks. This is particularly true for long-term investors who can minimize their exposure to market volatility and avoid buying based on emotion and reacting to market downturns in a panic.
Taking the psychological factor of investing into consideration please provide your own opinion, including some references and research based justification for the following question:
How might an investor's portfolio have changed from 1995 to 2000 if the investor had become overconfident? Give examples of the numbers and types of stocks in the portfolio.