On Good Judgment and Decision-Making: The Science and Practice

Imagine you’ve made two decisions. One has resulted in a loss of 10 thousand dollars, while the other resulted in a gain of 10 thousand dollars. Would you say that the former was a bad decision, and the latter was a good one?

The first response that usually comes to everyone’s mind is “of course, the second decision was better”. But this is not necessarily the case. Can you think of a scenario where your response would be the opposite?

I’ve been thinking and reading about decision-making for many years while trying to put everything I learned into practice. Below, I summarize the strategies and mental models that I personally found most useful.

The Process vs. The Outcome

We all have a natural tendency to judge decisions based on their outcomes. This is not the worst heuristic, as there is a correlation between the quality of decisions and outcomes. But this heuristic has a major flaw — it doesn’t account for luck and incomplete information.

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Mental Math: Years to Double an Investment

Sharing a very simple, but handy mental math rule that was mentioned in quite a few of our MBA classes, such as Investment Styles and Strategies, Designing Financial Models that Work and others:

If you want to quickly ballpark the # of years it will approximately take for an investment to double, then just divide 72 by the annual growth rate. For example, if your investment grows 7% a year, it will take slightly more than 10 years for it to double (72/7). But if it grows 36% a year, it will only take about two years to double (72/36). 

You can read more about this “Rule of 72” on Wikipedia. Now, you now you can come across as a math genius without much effort 😉