Here in the United States, there's well-publicized research into how hard many families would have to work to come up with the money to cover an unexpected $400 expense.
I didn't see anything about how much they would have to work, just what percentage would have trouble coming up with the money on short notice. It doesn't even imply they are poor, they could simply put all their money into their mortgage every month.
https://www.federalreserve.gov/publications/2019-economic-we...