Beware rushing to conclusions about which policies are best for defeating coronavirus

Despite recent remarks from Sweden's chief epidemiologist, attempts to identify a dominant policy explanation for the variation in excess deaths between countries are not (yet) convincing, writes Ben Chu

'If we would encounter the same disease, with exactly what we know about it today, I think we would land midway between what Sweden did and what the rest of the world did,' Dr Tegnell told a local radio station (Getty)

Natural scientists run experiments in a laboratory to test their hypotheses. Imagine you’re a biologist and you want to see the impact of rising temperature on the growth of a strain of bacteria? Take two samples, heat one but not the other, and observe the results. But social scientists lack that ability to test their ideas about the effectiveness of various social policies in a lab. You can’t put two countries on petri dishes and inject them with different policies.

That’s why social scientist are always on the hunt for so-called natural experiments. Think of two similar countries. One imposes a ban on smoking indoors while the other doesn’t. What subsequently happens to overall cigarette sales in both?

Consider two adjacent US states. One hikes the local minimum wage significantly while the other keeps its own steady. What then happens to the rate of unemployment in each? Such natural experiments are immensely valuable to researchers as a source of empirical (as opposed to theoretical) evidence for what works and what doesn’t when it comes to policy.