Extreme Concentration of Ownership in the United States The Oligarch Take over of Healthcare and Big Pharma A close-knit oligarchy controls all major corporations. Institutional investors like BlackRock, Vanguard, State Street, Fidelity, and JP Morgan, now own 80% of all stock in S&P 500 listed companies. The Big Three investors BlackRock, Vanguard and State Street alone constitute the largest shareholder in 88% of S&P 500 firms, which roughly correspond to Americas 500 largest corporations.