Sean Markowicz, CFA Strategist Schroders sees a very small group of mega tech companies having a very big influence. This regarding to variables like their stock market returns, revenues and net profits. Passive investors made very huge gains with these super stars stocks. But yesterday's winners won't surely be tomorrow's winners Markowicz warns. The high concentration by just a few companies causes higher investment risks according to Markowicz. Some of the current super stars companies are Amazon, Apple, Alphabet, Facebook and Netflix. Markowicz warns that the tide could turn, mostly because of regulatory issues but on the other hand most of these companies have very strong positions and difficult market entries.