Simple. The fundamentals. If the guaranteed return is less than or equal to the earnings per share, then the game can continue indefinitely. Index funds don'

Simple. The fundamentals. If the guaranteed return is less than or equal to the earnings per share, then the game can continue indefinitely. Index funds don't have gains because people keep believing the price will increase. They have them because the market as a whole gains in the long run. Index funds lose value during market downturns. Anyhow, no index fund offers guaranteed returns. These days I only see that from crypto ponzis.