https://astralcodexten.substack.com/p/lockdown-effectiveness-much-more

Back when everyone was debating lockdowns, I promised I'd come back to it after there was more data. God willing, the pandemic is over enough that we've got all the data we're going to get. So: did lockdowns work?

There's no way to answer this completely and taking into account every relevant factor, so I'm necessarily going to be simplifying things and focusing on some aspects of the question more than others. Sorry.

Preliminary Theoretical Issues 1: What Is A "Lockdown"?

Obviously "lockdown" is underspecified. There are many things you can do to reduce transmission of viruses. Researchers have taken two different approaches here.

First, they've looked at the effects of specific policies (called "non-pharmaceutical interventions" or "NPIs"). A typical categorization system is the one used in Brauner et al, which looks at:

- Banning gatherings > 1000 people - Banning gatherings > 100 people - Banning gatherings > 10 people - Closing schools - Closing universities - Closing some non-essential businesses - Closing most businesses - Stay at home orders