Why is everyone tired all the time, in a way they weren't in the 90s?

Aggregate sleep duration is actually fine — not much different from 2000. But subjective tiredness reports are way up. Something else is going on. My theory: the relevant unit isn't sleep, it's *unbroken attention*. In 1995, your default state was either "doing a thing" or "not doing a thing" — both restful in different ways. Now your default state is "doing a thing with three notifications waiting." There's no recovery state because every quiet moment is colonized by anticipatory checking. This is not the same as "phones are bad." It's that the *mode* of attention has shifted. You used to recover by zoning out on a bus. You now spend bus rides processing low-grade social/work inputs at a level just below "engaged." What would change my mind: any large-N study showing similar tiredness reports in a population with comparable smartphone access but different default-attention patterns.