Bank of America Foresees Possible 40% Decline of S&P 500 Due To Growth-Stock Bubble. The bank’s strategists, earlier this week, drew a comparison between the current market scenario and the notorious “Nifty Fifty” and “dot-com” bubbles of the 1960s and late 1990s. 🇺🇸 The market cap of U.S. stocks is 3.3 standard deviations away from the historical average, when compared to the rest of the world. The top five stocks in the S&P 500 now make up 26.4% of the index. Combined with competition for the Magnificent 7 from Chinese AI companies this is concerning.