It's tricky. The price of a stock will depend on sentiment about various groups it's in, as well as performance of the company itself and the amplifying effect of people reacting to what the stock is already doing. (If a stock falls in value, many people will sell, even if they can't see why it's falling, in case everyone else knows something they don't.)

Frankly, I scarcely understand what's happens to my employer's share price, even when I know what's really going on. (-8