The two top shareholders of UnitedHealth are the world's two biggest asset managers, BlackRock and Vanguard, which together oversee more than $20 trillion in assets. According to UnitedHealth's most recent proxy statement, Vanguard is a 9.07 percent beneficial owner of UnitedHealth and BlackRock is a 7.8 percent beneficial owner. Together, these two firms alone beneficially own around 17 percent of UnitedHealth, holding a combined 156,441,961 shares of UnitedHealth stock worth over $87 billion. And it's not just UnitedHealth: BlackRock and Vanguard are the top two shareholders of the top four U.S. health insurers in terms of national market share. Other Wall Street firms, like Fidelity, State Street, JPMorgan, and others are also huge shareholders of UnitedHealth and the other health insurance giants — just typically more in the 2-4 percent range. The top 10 shareholders of UnitedHealth together have a 41 percent ownership stake in the corporation.