Summary: How big is the market? S&P 500 Market Cap. Source: Bloomberg That depends on what you mean by the market. The US stock market is worth about $20 trillion. That’s the value if you add up all the shares traded times their market price – the market cap of the S&P 500. When you divide the market’s total value by the total earnings (and losses) produced by those companies, you get the market’s PE ratio—a basic measure […]
