The UK's (political) coronavirus gamble
It's a good thing that we have an experiment running. By taking a different course, the UK will either validate or improve the rest of the world's response.
The aim is to flatten the peak enough to keep healthcare services running, while achieving herd immunity.
The reason for this is that the second wave of a pandemic can be worse than the first, as illustrated by this graph of the 1918 pandemic death rate.

There are arguments for and against this approach. Perhaps the most alarming argument against it is the fact that we probably cannot flatten the curve anything like enough to prevent overwhelming the healthcare system. Usually the graphs we are shown that illustrate how the curve might flatten so we can cope with the outbreak while we wait for herd immunity don't have any numbers on. Here's an example from Vox:

Joshua Bach has done some work trying to estimate how much flattening the USA would need, based on capacity levels in the healthcare system, numbers of ventilators etc, and the best available data on the hospitalisation rate. Obviously we won't know the answer until later on, but based on the data we do have, he concludes:
"Dampening the infection rate of COVID-19 to a level that is compatible with our medical system means that we would have to spread the epidemic over more than a decade! ... Containment is unavoidable, and should not be postponed."
That's way different to the impression given by the graph above.
There is also a political argument against the herd immunity approach. The UK government is assuming that the death rate won't spike so much in the short term that this strategy becomes politically unfeasible. Do they know how many people can die before they lose public support?
Johnson has bet his political farm on the NHS. If this approach to the virus means we end up with a health service that can't treat people or has to make decisions about who gets priority, like Italy whose trajectory we are almost following, he will have to manage the political consequences.
By the time we have hospitals overwhelmed, an escalating death rate and are accepting medical supplies from China, as the US is doing, Johnson's voter base may be disillusioned. It also won't help if the countries of the EU such as France, who have taken a different approach, are seeing better outcomes.
And there is no reason to be optimistic about NHS capacity. Sam Ashworth-Hays has the numbers. Already, 80% of intensive care bed are occupied. As Sam says:
It seems plausible that a majority of the deaths we will see will follow because the virus has the capacity to collapse the health system.
Italy is already triaging patients, and the UK’s 2011 pandemic preparedness strategy suggested that in a high impact scenario of the sort we might expect to see that this would follow.
This inevitably means that unless the governments' strategy reduces the peak significantly, more people will die than might have done in the short term.
If every hospital bed were turned over to treating coronavirus patients, and another 100,000 conjured up from nowhere, we would still be well short of the required total.
Of course, this might mean fewer people die long term. That seems to be the implication of the government's strategy. And Robin Hanson thinks that herd immunity is the only sensible policy precisely in order to make sure we don't have a resource crisis later on.
Even with unusually strong quarantine efforts, COVID-19 currently seems to be escaping from its initial region and nation, doubling roughly every week. Even if that growth rate falls by a factor of three on average, it will reach most of the world within a year.
At which point roughly half of the world who isn’t immune gets infected over a perhaps two week period. Medical resources are completely overwhelmed, so ICUs save only a few. And the world economy takes a huge hit; for perhaps months before that point most workers have stayed home from work in an eventually futile effort to avoid exposure. At the worst possible moment, food, trash, cleaning, heating, and cooling may be scarce, increasing the fraction of sick who die.
Boris will need to stick to his policy no matter how difficult the political position gets. The benefit of a herd immunity strategy is 'to increase the average resources available to help people recover when they are sick', as Robin Hanson says. Boris will need to make that feasible by increasing the supply of medical resources as much as possible and by finding a message that is palatable to voters.
But the UK government is taking a political gamble. If we accept the behavioural science assumption that people would prematurely get bored of self-isolation it seems reasonable to assume they will also lose patience with a higher death rate than other countries.
However much sense it makes to pursue herd immunity is a different question from whether it is politically acceptable to deliberately increase the infection rate now relative to what it could have been. Utilitarianism is all well and good, until people's relatives start dying.
And the gamble is not just that people will tolerate a higher-death rate for long enough to see the benefits of a herd immunity strategy. If the world enters a difficult recession, we will then be asking people to tolerate two horrible things.
It's not clear that behavioural science would know what to do if we reached a point where unemployment was rising, the UK death rate was higher than the EU death rate, and the NHS was unable to treat elderly patients.
And if the plan doesn't work and the healthcare system is overwhelmed do we have a back-up? Right now, as Rob Wiblin thinks, it may be the case that we can massively lower the infection-per-person rate with containment. Later on, we might have to use more extreme measures, like a shut-down.
One Twitter user has said: 'In a month there could be more ventilators. Chloroquine and remdesivir might be proved out. We might have learned about aftereffects in even young recoverees. Waiting a month to try for herd immunity might be wiser. We're on a learning curve.'
Let's hope the gamble works.