I think zero-sum was meant from a perspective of a fixed-resource being divvied up among more and more people. In that case each person gets a smaller and small

I think zero-sum was meant from a perspective of a fixed-resource being divvied up among more and more people. In that case each person gets a smaller and smaller theoretical share. Any exchange is locally fair but globally everybody is becoming worse and worse off. This is especially true if you disconnect the concept of living in your own home from the investment opportunity. I doubt many people are going "Sorry honey, we cannot afford a house now or probably ever, but hey that's fair because if we could afford it with so little money we'd be getting access to an unreasonably good performing investment and that wouldn't be fair to others." I think most (reasonable) renters would settle for significantly worse performing housing market in exchange for cheaper housing so that they could transition from renting to owning.