The place I got this statistic (or something like it) from was the RescueTime blog. Here is the easiest-to-find post I could find in 60 seconds making the claim, and other blogposts might poke at it more.
The most relevant quote:
One of the biggest mistakes so many of us make when planning out our days is to assume we have 8+ hours to do productive work. This couldn’t be further from the truth.
What we found is that, on average, we only spend 5 hours a day working on a digital device.
And with an average productivity pulse of 53% for the year, that means we only have 12.5 hours a week to do productive work.
I’m hoping for something that can definitively say “productivity drops after N hours”, or at least examines that question, rather than “we checked and people only do N hours of work/day”. Maybe people can do more than N if they feel like it, in which case it’s not a matter of how much the brain is capable of but of motivation.
I recall seeing studies making more concrete claims about burnout, overtime, etc, which seem more like what you were claiming. I can’t do more than google randomly for such studies at the moment which seemed less useful. I also don’t recall those studies matching the claims about 4 hours in particular.
(That said, another source of the four-hour thing is the book Peak, which claims you get four hours of deliberate practice a day, which is a somewhat different claim)
But note that RescueTime’s data only covers time spent on a computer, which is only a subset of productive work time; there are also meetings, work on paper, and things like that.
The place I got this statistic (or something like it) from was the RescueTime blog. Here is the easiest-to-find post I could find in 60 seconds making the claim, and other blogposts might poke at it more.
The most relevant quote:
I’m hoping for something that can definitively say “productivity drops after N hours”, or at least examines that question, rather than “we checked and people only do N hours of work/day”. Maybe people can do more than N if they feel like it, in which case it’s not a matter of how much the brain is capable of but of motivation.
Nod.
I recall seeing studies making more concrete claims about burnout, overtime, etc, which seem more like what you were claiming. I can’t do more than google randomly for such studies at the moment which seemed less useful. I also don’t recall those studies matching the claims about 4 hours in particular.
(That said, another source of the four-hour thing is the book Peak, which claims you get four hours of deliberate practice a day, which is a somewhat different claim)
But note that RescueTime’s data only covers time spent on a computer, which is only a subset of productive work time; there are also meetings, work on paper, and things like that.