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Biases That Cause You To Make Mistakes

You are your own worst enemy.

Those are the six most important words in investing. Shady financial advisors and incompetent CEOs don’t harm your returns a fraction of the amount your own behavior does.

Here are 15 cognitive biases that cause people to do dumb things with their money.

1. Normalcy bias
Assuming that because something has never happened before, it won’t (or can’t) happen in the future. Everything that has ever happened in history was “unprecedented” at one time. The Great Depression. The crash of 1987. Enron. Wall Street bailouts. All of these events had never happened… until they did. When Warren Buffett announced he was looking for candidates to replace him at Berkshire Hathaway, he said he needed “someone genetically programmed to recognize and avoid serious risks, including those never before encountered. Someone who understands normalcy bias, in other words.

2. Dunning-Kruger effect
Being so bad at a task that you lack the capacity to realize how bad you are. Markus Glaser and Martin Weber of the University of Mannheim showed that investors who earn the lowest returns are the worst at judging their own returns. They had literally no idea how bad they were. “The correlation between self-ratings and actual performance is not distinguishable from zero” they wrote.

3. Attentional bias
Falsely thinking two events are correlated when they are random, but you just happen to be paying more attention to them. After stocks plunged 4% in November 1991, Investor’s Business Daily blamed a failed biotech bill in the House of Representatives, while The Financial Times blamed geopolitical tension in Russia. The “cause” of the crash was whatever the editor happened to be paying attention to that day.

4. Bandwagon effect
Believing something is true only because other people think it is. Whether politicians or stocks, people like being associated with things that are winning, so winners build momentum not because they deserve it, but because they’re winning. This is the foundation of all asset bubbles. (more…)