Exponential growth bias: the numerical error behind Covid-19


Imagine being offered a deal with your bank, where your money doubles every three days. If you only invest $ 1 today, approximately how long will it take you to become a millionaire?Would it be a year? Six months? 100 days?

The exact answer is 60 days from your initial investment, when your balance would be exactly $ 1,048,576. In another 30 days, you would have earned over $ 1 billion. And by the end of the year, you would have over $ 1,000,000,000,000,000,000,000,000,000,000,000,000,000 – an “indecillion” of dollars.

If your estimates were irrelevant, you are not alone. Many people consistently underestimate the rate at which value is increasing – a mistake known as “exponential growth bias” – and while this may seem abstract, it may have had profound consequences for people’s behavior this way. year.

A series of studies have shown that people susceptible to exponential growth bias are less concerned about the spread of Covid-19 and less likely to approve of measures such as social distancing, handwashing or wearing a mask. In other words, this simple math error could cost lives – meaning correcting the bias should be a priority as we try to flatten the curves and avoid the second waves of the pandemic around the world.

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To understand the origins of this particular bias, we must first consider different types of growth. The best known is “linear”. If your garden produces three apples a day, you have six after two days, nine after three days, and so on.

Exponential growth, on the other hand, accelerates over time. Perhaps the simplest example is population growth; the more people you have that breed, the faster the population grows. Or if you have a weed in your pond that is tripling each day, the number of plants may start out low – only three on day two and nine on day three – but increasing rapidly (see diagram below).


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