[Bank of America is firmly bullish: there is no sign of a foam in the US stock market. This bull market still has stamina!] The "surge" of the US stock market has led many investors to put forward the "foam theory". They believe that the stock market has risen too much, too fast and is approaching the foam region. But Bank of America pointed out that there is almost no evidence to support these concerns. Bank of America strategists led by Savita Subramanian have stated in their latest report that although the US stock market has been strong since last year, it has not reflected the previous boom and bust cycles, such as the huge gap between stock prices and their value, or the excessive use of leverage.