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Thinking exponentially and the rule of 72

I came across the above Twitter thread last night before bed and I thought it was great. It’s about the importance of thinking exponentially, as opposed to linearly, when it comes to finance and investing.

In it, the author provides a quick rule of thumb to help reframe our mind when it comes to compounding. It’s called the “rule of 72” and it works like this.

To calculate the approximate number of years to double your money, simply take 72 and divide it by the annualized rate of return (%). For example, if you had an annualized rate of return of 10%, this rule of thumb would tell you that you’re going to need 7.2 years to double your money.

If the annualized rate of return were to increase to 18%, it would now only take you 4 years to double your money. Of course, this rule of thumb is an approximation. It only really works within a certain band of returns.

If the annualized rate of return were 100%, this formula would spit out 0.72 years, whereas an annualized rate of return of 100% actually means that you’re doubling your money in the span of one year.

It’s a rule of thumb. The reality is that compound returns are incredibly powerful over the long-run, not only for finance and investing, but for life in general. Worthwhile things take time. If you’ve got the patience and discipline, the long-run curve ends up looking pretty sweet.

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