This chart tracks the 'single greatest predictor' of stock-market returns — and it's never done this before - MarketWatch## Mark Hulbert# This chart tracks the 'single greatest predictor' of stock-market returns — and it's never done this before## Individual stock ownership is a contrarian indicator. It's flashing a warning.Published: Jan. 27, 2026 at 8:05 a.m. ETShareResizeU.S. individual investors now have more than half of their portfolios in stocks — a troubling sign. Photo: MarketWatch photo illustrati ...