The magical dynamics of exponential growth can lead to wonderful things when it come to GDP per capita-- Japan, South Korea, China and other "growth miracles." Sadly, however, exponential growth is entirely a curse when it comes to infectious diseases. The same mathematical forces that led us to conclude "growing at a rate of 2% per year, the U.S. can double GDPpc in approximately 35 years" also implies that in the early days of the pandemic, cases were doubling every 3 days. Exponential growth doesn't seem so groovy anymore, huh?
This week a study by researchers at the Columbia's public health school found that 36000 deaths could have prevented if social distancing measures had been implemented one week earlier than they actually were. Two weeks earlier, 54000 (84% of deaths). Changing the rate of growth (how many infections spread from person to person) at the right time has a dramatic effect on the subsequent dynamics.
By the way, a common mistake is using the word "exponential" interchangeably with "rapid." This is not always the case! "Exponential" simply means that some quantity increases in proportion to its current size. Depending on what your point of reference is, this increase in quantity may or may not be fast. This article from The Conversation does a super job in breaking down exponential growth not only in the context of COVID19 but also money, pyramid schemes and nuclear reactions.
Mathematics is very clear-cut about how, given certain parameters, a quantity will grow. But turns out human psychology is more fuzzy and human intuition has a hard time realising exponential growth:
This week a study by researchers at the Columbia's public health school found that 36000 deaths could have prevented if social distancing measures had been implemented one week earlier than they actually were. Two weeks earlier, 54000 (84% of deaths). Changing the rate of growth (how many infections spread from person to person) at the right time has a dramatic effect on the subsequent dynamics.
By the way, a common mistake is using the word "exponential" interchangeably with "rapid." This is not always the case! "Exponential" simply means that some quantity increases in proportion to its current size. Depending on what your point of reference is, this increase in quantity may or may not be fast. This article from The Conversation does a super job in breaking down exponential growth not only in the context of COVID19 but also money, pyramid schemes and nuclear reactions.
As Benjamin Franklin put it: “Money makes money, and the money that money makes, makes more money.” If you could wait long enough, even the smallest investment would become a fortune. But don’t lock up your rainy-day fund just yet. If you invested £100 at 1% per year it would take you over 900 years to become a millionaire. Very few people would accuse the exponential growth associated with their bank account of being large or rapid.Doesn't it feel a bit unfair that money growing exponentially is not nearly as dramatic as a deadly virus growing exponentially? Reassuringly though, the growth that characterizes the early days of a pandemic does not last forever, and many efforts to flatten the curve are achieving that goal.
Mathematics is very clear-cut about how, given certain parameters, a quantity will grow. But turns out human psychology is more fuzzy and human intuition has a hard time realising exponential growth:
A cognitive bias that puzzles millions of people in home-isolation around the globe is the exponential growth bias. Our brain is not wired to think in exponential terms. We can easily estimate where we will get if from our front door, we take 30 steps, but we cannot estimate how far we will get if we take 30 exponential steps [2], that is, double our step each time. 1+2+4+8+16. The answer is, we’d go around the globe 26 times! Exponential growth bias makes it very hard for citizens to evaluate the status of the pandemic in their countries.Discussion Questions
