“On Day 1 you start with 1 penny. On Day 2 you double it and have 2 pennies. On Day 3 you double that and have 4 pennies. Repeat. How much money do you have on Day 30?”

Most people have been asked this question at one point or another.

It’s memorable; in part because the idea of doubling the size of your bank account day after day sounds like something you’d sign up for.

But what usually sticks the most is how surprising the answer might be:

On Day 30 you’d have **$5.37 million**.

What? 1c becoming millions of dollars that quickly? But after untangling the branches, the math checks out.

*Doubling over and over for 29 days?*

*2 ^{29}*

Things make a little more sense one we’re able to localize to what’s familiar: powers of 10.

COVID-19 is another one of these tricky situations. How bad will it be? Am I at risk? Should I hole up in a cabin in the woods for the next X weeks? How will our infrastructure handle the increasing number of cases? How do we prevent another Wuhan, or worse?

It doesn’t help that social media and news outlets are ablaze with so many varying opinions.

What does help is localizing. Untangling the branches, going back to what’s familiar: math and science.

To put COVID-19 in a base-10 perspective:

The number of new COVID-19 cases doubles every 7 days.

**That’s equivalent to 10x-ing every 23 days.**

**Or 100x-ing every 1.5 months.**

*Assume there are 2,000 cases in the US today, on March 5.*

*(conservative IMO given the lack of test kits available)*

*By March 28 - 20,000 cases.*

*By April 20 - 200,000 cases.*

*By May 13 - 2,000,000 cases.*

What do we need to do now to prepare for 100x the volume in the next 1.5 months, and beyond?

By now we’ve been inundated with directives to “wash your hands for 20s”, “don’t shake hands”, and “avoid touching your face”. (Like that last one is even possible.)

But what does that really do? What effect will that have against a virus that’s 10x-ing every few weeks?

Well much like how exponential growth works in the spreading of the virus, it also works in the mitigating of it.

First off, you lower your own chances of getting sick.

And the important part, especially for younger people? You lower your chances of being hospitalized.

Dr. Fauci confirms that around 20% of #coronavirus patients require hospitalization. That's the crux of the problem. Our hospitals don't have this capacity.

— Karen Piper (@PiperK) February 29, 2020

Probably the single most important headline this week:

— Luca Dellanna (@DellAnnaLuca) March 1, 2020

- After just one week from the outbreak, Northern Italy is already considering expanding its hospital beds capacity because 1 in 11 patients goes in ICU

Now this is where the second-order effects bring exponential power.

By lowering your own chances of getting sick and reducing contact with others, you slow the rate of the virus’s spread. We can significantly “flatten the curve”.

If we reduce the spread, even if we ultimately have the same total number of cases, we 'flatten the curve,' which means that, at any given time, our health care system can cope with the COVID-19 cases, hopefully. 2/ pic.twitter.com/PlaRIyc94r

— Nicholas A. Christakis (@NAChristakis) March 3, 2020

One big result: **we significantly reduce the number of people needing hospitalization at the peak**.

And alleviate pressure on our public systems to handle the urgent cases.

Bringing it back to base-10: if the virus were to take 10 days to double instead of 7, that’s equivalent to 10x-ing every 33 days. *That’s already 50% longer*.

So thank you for washing your hands. You’re helping save lives.

Here are some highlights from people who recognize the exponential growth at play: sharing info, asking questions, and taking action.

Extra reading: Tyler Cowen on the “growthers” and “base-raters”, the different camps discussing the growth rate of COVID-19.

Drop a reply, or just come say hi here!