Phil Anderson wrote an interesting article in the Duluth Reader about the linkage between the Brexit vote and the reactions of stock markets. See
I’ve often wondered how the stock markets could turn on a dime based on some event or another. It seems more that commentators need to justify their salaries rather than provide insight for investors. Oops! That should be traders! Anderson describes investors those who are in for the long haul. Traders now will sell stocks within seconds of buying them.
I remember crossing the old Broadway bridge over the Mississippi River in the late ‘70s when the market news was a new high on the New York Stock Exchange of 54 million shares. Today, 2016-07-13, the NYSE volume was 836,762,854 shares; a week ago it was 1,050,701,150 (Wall St. Journal, http://www.wsj.com/mdc/public/page/2_3021-tradingdiary2.html). That’s about 20 times what it was over 30 years ago. Probably the big difference is online trading, then you had to call your broker who then placed the order on a teletype.
Still, I agree with Phil Anderson, how can so many people be in lockstep because of certain events?