Bloomberg Markets stressed that point this morning:
"There appears to be an unusually tight correlation between China's PPI and the S&P 500's performance in recent years. When China's factory prices started to rise from a deep deflationary spiral in early 2016, it also marked the trough of the S&P 500 that year. In fact, the correlation between year-on-year change of the S&P and China's annual PPI over the past three years amounted to a rather high reading of 0.77."
"While the U.S. economy is benefiting from a robust labor market and resilient business confidence, it's hard to argue that it can be completely isolated from the slowdown of the world's second largest economy."