Returns to the S&P should beat GDP growth even in the long run, steady-state. GDP growth flows to both debt and equity. The debt market is actually much larger

Returns to the S&P should beat GDP growth even in the long run, steady-state. GDP growth flows to both debt and equity. The debt market is actually much larger than the equity market and since its returns are lower than equities, and they both share GDP as a source of returns in the long run, equities should beat GDP growth in the long run. This argument isn't iron clad, but hopefully you can see the general picture. The Gordon growth formula is taught in intro to finance classes to estimate returns to equity. The theory is that stock market returns equal the dividend yield plus growth in stock prices. Stock prices alone are in the long run expected to grow at the same rate as GDP, but the actual return should be higher by the rate of the dividend yield. These are the most basic arguments against what you're saying, but I would also caution against assuming that any particular macroeconomic trend will end, especially that it will end in a timeframe relevant to decisions related to solar panel installations. Sometimes they just keep going. There is no mathematical reason that equity prices can't go to infinity, as required rates of return can decrease to zero. If the world becomes more predictable and stable, equities can keep becoming more and more valuable with no damage to finance theory.