Fear and the exponential function

Courier article

“The greatest shortcoming of the human race is our inability to understand the exponential function.” So says Al Bartlett, a now retired US professor of Physics, who has given the same talk on this topic nearly two thousand times over the last forty years. I think he has a point, and I’d like to explain why, with particular reference to the Ebola epidemic now taking root in West Africa.

A quick refresher on the exponential function – that is, on what it means when something grows exponentially. Exponential growth occurs whenever something grows at a constant rate – for example, an economy that is growing at 5% a year. So if we begin with 100 widgets of production, and our production grows by 5% then after 1 year we will have 105 widgets. If the growth continues then after another year we will have 110.25 widgets. After another year we will have 115.7625 widgets. Notice that the amount added on increases each time – 5 widgets in the first year, 5 and a quarter in the second year, five and a half in the third year. That is because the underlying quantity has increased. So exponential growth is not simply adding on a fixed amount each year, it is adding on an increasing amount each year.

The interesting thing about exponential growth, and what makes it so marvellous and miraculous and devastating, is something called ‘doubling time’. When a certain percentage of growth is maintained over time then we can expect the underlying quantity to double at a particular rate. For example, if growth is maintained at 7.5% a year then the underlying quantity will double (approximately) every ten years. This is well understood in financial circles, and is seen as the ‘miracle of compound interest’, whereby your bank balance – at least when interest rates are higher than they are at the moment – increases significantly year on year, so long as it is left untouched.

The reason why I want to talk about the exponential function again is because I see it as extremely relevant to understanding why the Ebola epidemic is such a cause for concern. I want to argue that we need to be a little more frightened than we are at the moment, in order that we end up being much less frightened overall. I’m sure we are all familiar with the nature of the Ebola virus, and the ghastly death that it causes in the majority of people who have succumbed to the disease. What seems to be less widely understood is that the number of people who are becoming infected with the disease is growing exponentially, with a ‘doubling time’ of around three weeks. If the virus is left to grow in the human population unchecked, then we are looking at some very scary projections. The trouble is that so far our political responses seem to be marked mostly by complacency.

It has been assumed that Ebola would not be able to spread rapidly in a Western country, due to our highly advanced health systems, and also to what might be called either a ‘scientifically informed common sense’ or a ‘reasonable sense of disgust’. There are particular cultural habits in West Africa which have enabled the virus to spread more rapidly, especially due to funeral practices, and even if we had similar habits in this country, I think that we would let go of them quite rapidly once we understood that they enabled the disease to spread. However, as I write this column there is coverage from Texas of an outbreak of Ebola there, where it would seem that best practice was not followed, even in an advanced hospital. I shall continue to watch with interest to see how widespread the infection becomes.

Have you ever watched one of those movies that is about an epidemic, where the senior ‘man in charge’ of the US response starts telling people what is going on, and how scary it is? Well that person in real life is called Tom Frieden, and he is the Director of the US Center for Disease Control and Prevention. He recently said this: “The speed at which things are moving on the ground, it’s hard for people to get their minds around. People don’t understand the concept of exponential growth. Exponential growth in the context of three weeks means: ‘If I know that X needs to be done, and I work my butt off and get it done in three weeks, it’s now half as good as it needs to be.’ ”

Put simply, if we are to ensure that this outbreak of Ebola is contained, we need to take much stronger and sterner measures at an early stage. We need to contain the outbreak and prevent it from expanding, and such measures would include (for example) establishing strict quarantine measures for any travellers coming to this country from West Africa. Such a process would undoubtedly be a cue for squeals of outrage from the politically correct, and would be denounced as ‘racist’ and (much worse) profoundly inconvenient for those who want to take advantage of air travel around the globe. I think that such things are luxuries, and if we are to prevent a serious health crisis in our own country, we need to take much more direct measures immediately. A few weeks of extra hassle and fewer options is a small price to pay set against the horror and squalor than an uncontrolled outbreak would bring.

What we face with the Ebola crisis (at least for those of us who live in the rich West) is not necessarily an existential crisis. There is no element of the disease that cannot be handled by our health care and social welfare systems – so long as we act in good time, with all proper caution and due diligence. Where my concern lies is not in our physical capacity to deal with this, but with our decision making processes, that is, with the political leadership that we presently endure – and that is not a point about a particular person but about the quality of the political class as a whole. My fear is about their fears – that they are more afraid of short-term unpopularity brought about by seeming politically incorrect and draconian, rather than being afraid of what the unchecked exponential growth of a contagious disease will cause. As another US expert has put it: “The virus is moving on virus time; we’re moving on bureaucracy or program time.” That’s not good enough.

(Quotations found here)

One thought on “Fear and the exponential function

  1. Judging by this Guardian article, your fears may be justified:

    “Ebola now functions in popular discourse as a not-so-subtle, almost completely rhetorical stand-in for any combination of “African-ness”, “blackness”, “foreign-ness” and “infestation” – a nebulous but powerful threat, poised to ruin the perceived purity of western borders and bodies. Dead African bodies are the nameless placeholders for (unwarranted, racist) “panic”, a conversation topic too heavy for the dinner table yet light enough for supermarket aisles.”

    The problem with the west’s Ebola response is still fear of a black patient

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