The shares had such a huge run up this year it is simply time for them to retrace a bit. Volumes low in Dow SnP, many traders on vacation, the banker buffoons threatened a hawkish rate increase, gold investors not investing until after Janet Yellen’s speech Friday.
Markets dropping like this? During their meeting is good, it will scare them (or give them excuse) to make a dovish (no rate increase) announcement. They are data dependent, depend on data for decisions, but they themselves create the data with their stupid announcements.
TPTB like to use child psychology on the markets.