Krugman: When do events tell us that we need a fundamental rethink of economic concepts?

Essentially nobody saw the 2008 financial meltdown coming (other than people who predicted many other crises that didn’t happen), but when it did come, there wasn’t much existential angst among economists I talked to. 

We’ve long had a theory of banking crises; we just thought that regulations and deposit insurance made an old-fashioned wave of bank runs impossible — which they did, for traditional banks.

What few had realized, however, was that much of the modern financial system now involved “shadow banks” that did bank-type business but, because they weren’t marble buildings with rows of tellers, lacked both the regulations and the government guarantees that protected traditional banking. 

I consider MMT the cryptocurrency of macroeconomics:
It sounds edgy and forward-looking, but when you press its devotees on what exactly is its point, what it can do that you can’t do better using more conventional approaches, the response is a lot of bombast but no clear answer.

Paul Krugman New York Times 8 February 2022

https://www.nytimes.com/2022/02/08/opinion/economic-theory-monetary-policy.html

In the 1970s some economists began arguing that Keynesianism must be wrong, because ... Then came the 2008 crisis and its aftermath, which demonstrated that Keynes had been right all along. 

Paul Krugman NYT 1 June 2021

https://englundmacro.blogspot.com/2021/06/in-1970s-some-economists-began-arguing.html