> Is the positive impacts anecdotal?

No. Lack of commute is concrete and tangible. Even just from an emissions standpoint.

Decreased spending on office space is not anecdotal, but again concrete.

These are externalities to worker productivity, not necessarily correlates of it.

Agreed I've seen the following downsides first hand: * Lack of drive and motivation about the project. This drive doesn't isn't necessary to make folks work longer hours, but simply care more about wider impacts of choices they make. * Increased rate of depression. Human interaction and getting out of the house are important, and while in office work isn't necessary for this to occur, it's somewhat like paying off a low interest loan. You are more likely to do it and see the benefits than you are to invest the money you would have used into a higher yield investment vehicle. * Decreased physical fitness of my peers (they eat more poorly and perhaps a side effect of depression) * Lack of empathy for peers. Management just seems to be colder as they don't know their reports as well.

All of these have material impact on productivity, but more importantly healthy and happiness of employees themselves. The effects are not uniform, but there are tradeoffs and it's not clear to me that wfh is better for everyone.