The Covid pandemic poses a very interesting evidence-based policymaking challenge. Sorry, very busy, barely on twitter, but here's a mini splurge.

There are legitimate questions about the strengths and weaknesses of evidence for the impact of each option. How many lives will really be saved by “Stay At Home”? What is the medium- and long-term economic impact? Nobody can be absolutely sure on either of these numbers.

Then there are legitimate questions about which group to prioritise. Should we put lives first? Or the economic future of the nation? (And poverty kills too). There really is a hard trade off here. So who shall win, and who shall lose? To govern is to choose!

So far so commonplace: difficulties predicting the future; and difficulties choosing which groups to prioritise. But covid brings an extra glitch. Whatever choice is made, it affects us all, and we *all* have to stick with it, or everyone loses.

Collectively we chose total shutdown. We chose to endure the economic downturn, to save lives. If some people ignore the shutdown, then we will get the economic downturn AND the covid deaths too. (Thanks, saboteurs, we just got the worst of both worlds!).

In this context, national unity suddenly matters. We absolutely must debate the evidence. But whatever we decide, we then *all* need to cooperate, or we all lose. So, uniquely, I’m somewhat against the attacks on government for using PR gimmicks, PR experts, and bevavioural hacks

Because this time around, while debate is important and useful, more than in most other cases: it matters that everyone is bounced into playing along, or we get the worst of both worlds.

And for some, but not all, of the decisions being made, the importance of making a decision, and everyone sticking to it, is arguably as important as which specific decision is made.

You should hopefully know from the history of everything I’ve written that I don’t say these things lightly, or flippently. And I hope you also know that I don’t say them in a mood of capricious panic. I also don't want these principles extended to everyday life.

But I do think that evidence-based policymaking in the Covid pandemic is a weird, extreme, interesting case.

One more thing. I fully embrace everyone's right to dissent. I don't think one scientist making a silly claim about some evidence is the same as shouting fire in a crowded theatre. But it probably is worth being careful. Especially when we know some parts of the media can be dim.