The SPDR S&P 500 has been volatile since July 31, when the Federal Reserve released the FOMC Statement. The US policymakers provided in-depth insights into the economic and financial conditions that influenced their vote to lower the target range for the interest rate to 2% to 2.25%. Note that this was the first rate cut since 2008.
Another key factor that affecting the SPDR S&P 500 is the US-China trade tensions. For example, the exchange rate fund dropped 1.10% on August 1, when the US President Donald Trump announced that the US would impose 10% tariffs on $300B worth Chinese products starting September 1. The exchange rate fund appreciated 2.30% on August 13, when the US representatives declared that the imposition of additional tariffs would be suspended until December 15.
According to analysts, the SPDR S&P 500 could remain volatile, as the US-China trade war has been escalating. Meanwhile, the monetary policy remains unclear as the US policymakers are not able to catch up with developments of the ongoing trade dispute. This factor adds fuel to the fire.