That's the point about equity not being zero sum. The projects in the underlying businesses do create value over time which is shared with the owners. If the index rose 20%, someone who gained 15% with inflation at 3% and bonds paying 5% they are not a loser. They actually did quite well compared to the next best option they had.Therefore, I need to change my word. "Equity is zero sum with respect to index change"
For example, when index rise from 15000 to 18000, everyone wins 20% / Furthermore, anyone who win less than 20% during that time is actually loser.