There have been many important numbers in this pandemic but one has come to tower over the rest: the reproduction rate. The R number, as everyone calls it, has been used by the government to justify imposing and lifting lockdowns. Indeed while there are many important numbers — gross domestic product, parliamentary majorities, interest rates — few can compete right now with R. Which is why it’s strange that so little is ever said about what it actually is.
I don’t mean what it represents. As most of us know, R is an estimate, a range rather than a single figure, of how many people the average person with Covid passes the virus onto. Anything above one and the spread of the disease is growing;