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What is R? The transmission rate that will shape our future

Government policy is now focused on keeping the rate of coronavirus transmission, known as R, below one. What effect will this have on the UK's lockdown? 

By Stephen Bush

Boris Johnson has announced the government will publish its exit strategy, but that the United Kingdom will remain in something a lot like lockdown unless or until we can be certain that the transmission rate or R  remains below one. Distance working, phased re-opening of schools and mask-wearing in public places are all coming to the UK. 

What’s R, you say? Well, as Tony Yates puts it, the rate of R in human beings is at one when a couple has two children: the exact number to replace them in the general population. When R is below one (if people have fewer than two children) the population falls, and if R is above one (people have three, four or more children) then the population rises. 

Keeping R below one means that the number of cases of coronavirus will continue to fall, allowing the NHS to keep functioning and for people with other medical issues, and those waiting for elective or non-urgent surgery, to resume their treatment safely. 

That Johnson has opted to prioritise keeping R below one is a further indication of what his first public appearance suggested  that in the internal Tory battle over lockdown, he has opted to prioritise reducing new cases over reopening the economy; that he is preoccupied with making the United Kingdom function better in lockdown rather than ending it.

Keir Starmer, who made exit strategy his first big demand as Labour leader, was on the airwaves doing a “I was right – but I’m also constructive” dance. But now that the question is what the contents of the government’s plan will be, rather than whether to share it at all, who will emerge as teh better leader: him or Johnson?

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