America's S&P 500 and Nasdaq stock market indexes hit more than six-month lows on Monday. At 09:44 am (US time), the S&P 500 was down 81.90 points (1.47%) to 5,499.04 and the Nasdaq was down 409.48 points (2.36%) to 16,913.52. The indices fell amid massive selloff by investors on worries over US President Donald Trump's upcoming announcement of tariff plans.