At various times they call markets a “stock pickers market” meaning that if you could pick a decent stock out you would make money by going against the herd. At other times the whole market just moves in unison, meaning that whatever you pick (as long as the industry isn’t going down the drain) it doesn’t matter that much.
Yesterday this was the status of the 15 stocks in portfolio one. EVERY ONE of the stocks went down, and they represent a reasonably broad spectrum of industries and countries (US and overseas). On a grand scheme this happened when the market cratered in 2007-8; everything went down the drain but if you bought low at the nadir and held on the way up you basically doubled your money.
Co-variance is definitely on the rise, and US and foreign markets are generally moving together. There are always exceptions but when you see every stock moving in unison that is pretty much the definition of co-variance.