Tag - Outcome Bias

May 2017

Behavioural finance, Behavorial finance, Outcome Bias, Investing

Never Judge a Decision by Its Outcome: Outcome Bias

Never Judge a Decision by Its Outcome: Outcome Bias

A quick hypothesis: Say one million monkeys speculate on the stock market. They buy and sell stocks like crazy and, of course, completely at random. What happens? After one week, about half of the monkeys will have made a profit and the other half a loss. The ones that made a profit can stay; the ones that made a loss you send home. In the second week, one half of the monkeys will still be riding high, while the other half will have made a loss and are sent home.

And so on.

After ten weeks, about one thousand monkeys will be left—those who have always invested their money well. After twenty weeks, just one monkey will remain—this one always, without fail, chose the right stocks and is now a billionaire.

Let’s call him the success monkey.

How does the media react?

It will pounce on this animal to understand its “success principles.” And they will find some: Perhaps the monkey eats more bananas than the others. Perhaps he sits in another corner of the cage. Or maybe he swings headlong through the branches, or he takes long, reflective pauses while grooming. He must have some recipe for success, right?

How else could he perform so brilliantly? Spot-on for two years—and that from a simple monkey? Impossible!

The monkey story illustrates the outcome bias: We tend to evaluate decisions based on the result rather than on the decision process. This fallacy is also known as the “historian error.” (more…)