Another argument might be made that income variability is now more significant, as any break or disruption is likely to be highly disruptive: loss of housing, family relocation, disruption of children's education and environment, etc.

I'm notaware of any specific study of same, offhand,but the notion has a name: The precariate.

It's what Yonatan Zunger (not an economist) describes as "your financial shock wealth":

https://shift.newco.co/your-financial-shock-wealth-4845e6dc1...

"All hollowed out" does reference several related studies:

https://www.theatlantic.com/business/archive/2016/01/white-w...