Rewind a few weeks and most of us couldn’t spell epidemiologist, let alone name any. Now we all know who Neil Ferguson is. We are all familiar with the “R-rate”, herd immunity, isolate and trace, and other strategies for controlling the spread of diseases we hardly thought about before. It’s right that we should be. Covid-19 is a lethal disease that has already caused 30,000 deaths in the UK, 277,000 around the world, and has the potential to overwhelm societies if it is allowed to spread unchecked. To combat it, we need to listen to the scientists. This is not a time, to borrow a phrase from the Brexit debates, when we should have had enough of experts.
Forecasts are mostly useless
Yet we should not be blind to their failings. Let’s take a comparison with economists. We let the experts on supply and demand guide huge swathes of public policy. There are teams of them at the Treasury and even more at every think tank and investment bank. We generally put them in charge of our central banks and allow them to run monetary policy independently of the government or the electorate.
There is nothing wrong with that. Economics has lots of hugely useful insights. Left to themselves, markets usually solve most problems. Lower taxes sometimes generate more revenues. We should import stuff even if we can make it ourselves because it frees up resources to do other things. Governments can spend more than they raise in taxes, often for a very long time, and that can help fix recessions. And so on. None of those points are obvious and economists help remind us of them.
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But there are caveats. They are useless at forecasts. Even the most sophisticated central-bank model virtually never accurately predicts a recession. There are simply too many variables at play and the models are never sophisticated enough to capture all of them. And they are as guilty of groupthink as any other profession. Economists form a consensus and everyone signs up to it, even when there is far less evidence for it than they think.
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The same is true of epidemiologists. They have useful insights. They should be able to tell us how and where a virus is transmitted. They should be able to help work out who is most at risk. Rates of infection and the likely rise in cases should be roughly mapped out. But like the economists, they may turn out to be just as useless at forecasting because, as with the economy, there are too many variables at play for any model to be meaningful. Will everyone stick to the lockdown, or will a few people (including some high-profile epidemiologists) ignore it? Will social distancing be strictly observed at the shops that open? Change the percentage of people breaking the rules by a fraction of a point and you get a hugely different outcome.
Who are the cranks?
Epidemiologists too are subject to groupthink. A specialist academic discipline, with little movement between institutions, may well produce fine science. But it also creates a closed world in which assumptions are not questioned and everyone comes up with similar answers.
With epidemiologists there is another caveat. Economists have been subjected to public scrutiny for years. We have been judging their forecasts and predictions for a long time and running league tables of which ones are more accurate and which less so. We have a pretty good idea of who to listen to and who is a crank. By contrast, epidemiologists have been subject to little scrutiny. We don’t really know what their record is like – not that great, as it turns out – or which ones are really good.
We must learn to treat epidemiologists as we do economists. Listen to what the science has to teach us and accept many of its insights, perhaps most of all when they are not intuitively obvious. But we should also accept that they can’t forecast anything reliably and won’t ever be able to. We should be guided by what they have to say, but not to the exclusion of all other considerations. And we certainly shouldn’t put them in charge of the country.
