The crisis caused by the second wave of the Covid-19 pandemic has led to a revival of interest in mathematical models for the progression o...
The crisis caused by the second wave of the Covid-19 pandemic has led to a revival of interest in mathematical models for the progression of the pandemic. Several modellers have made public predictions for the size and duration of the second wave. These modellers suggest that they can predict the future, and their models carry the imprimatur of science. So it is natural that people are very interested in what they have to say.
However, we would like to explain why such predictions are often misleading. Mathematical models are used successfully in many branches of science. But the models that have been constructed for the pandemic suffer from serious theoretical problems and have a poor empirical record of predicting its course over the past year.
Modellers in India not only uniformly failed to anticipate the emergence of the second wave, there is no evidence that they now have the tools to understand its future trajectory. In some cases, not only do these models represent substantively poor science, they are promoted by modellers who have chosen to discard essential steps in the scientific procedure.
Compartmental models
The most commonly used models are called “compartmental models” and are constructed by dividing the population into groups. For instance,...
