Behavioral finance encompasses many concepts, but four are key: mental accounting, herd behavior, anchoring, and high self-rating and overconfidence.
Mental accounting refers to the propensity for people to allocate money for specific purposes based on miscellaneous subjective criteria, including the source of the money and the intended use for each account. The theory of mental accounting suggests that individuals are likely to assign different functions to each asset group or account, the result of which can be an illogical, even detrimental, set of behaviors. For instance, some people keep a special “money jar” set aside for a vacation or a new home while at the same time carrying substantial credit card debt.
Herd behavior states that people tend to mimic the financial behaviors of the majority, or herd, whether those actions are rational or irrational. In many cases, herd behavior is a set of decisions and actions that an individual would not necessarily make on his or her own, but which seem to have legitimacy because “everyone’s doing it.” Herd behavior often is considered a major cause of financial panics and stock market crashes.
Anchoring refers to attaching spending to a certain reference point or level, even though it may have no logical relevance to the decision at hand. One common example of “anchoring” is the conventional wisdom that a diamond engagement ring should cost about two months’ worth of salary. Another might be buying a stock that briefly rose from trading around $65 to hit $80 and then fell back to $65, out of a sense that it’s now a bargain (anchoring your strategy at that $80 price). While that could be true, it’s more likely that the $80 figure was an anomaly, and $65 is the true value of the shares.
High self-rating refers to a person’s tendency to rank him/herself better than others or higher than an average person. For example, an investor may think that he is an investment guru when his investments perform optimally, blocking out the investments that are performing poorly. High self-rating goes hand-in-hand with overconfidence, which reflects the tendency to overestimate or exaggerate one’s ability to successfully perform a given task. Overconfidence can be harmful to an investor’s ability to pick stocks, for example. A 1998 study entitled “Volume, Volatility, Price, and Profit When All Traders Are Above Average”, by researcher Terrance Odean found that overconfident investors typically conducted more trades as compared with their less-confident counterparts—and these trades actually produced yields significantly lower than the market.