Analyst: The decreased volatility of the S&P index indicates a weakening market momentum.

As of the close on Monday, the S&P 500 index has not seen a daily change of more than 1% for 18 consecutive trading days, marking the longest period of relative calm since December of last year. Matt Maley, chief market strategist at investment firm Miller Tabak, believes that this decrease in volatility indicates that the market's momentum is waning after a strong rebound following the lows triggered by tariffs in April.