The relatively large drop in today’s trading was attributed to a decrease in the reported consumer confidence (which is irrelevant) and China reporting lowered economic growth.
If you look at the Shanghai Index, you can see share prices are already ratcheted down since roughly in April. This also corresponds to the S&P 500:
I don’t have any strong opinions on the broad markets – I find the S&P 500 to be a fairly good screening tool, whereby I would not consider investing in an S&P 500 equity component unless if something really significant was going on that I thought the market had an incorrect take on. The last example I can think of was Philip Morris during the middle of the tobacco lawsuit settlements. Too much money is linked to the S&P 500 index so the equity is likely to be over-inflated. Not only that, but closet index funds do enough research on all of the components to make the markets relatively efficient, so it is generally worth spending your time on smaller and less liquid issues.
If growth in China, however, is slowing then you are going to see ripple effects in the marketplace.