BlackRock, Vanguard and State Street manage a stunning $15 trillion in combined assets, equivalent to more than three-quarters the size of the US economy.

The rapid growth of the Big Three fund managers, driven in part by rise of dirt-cheap ETFs, gives them enormous sway over financial markets and the priorities of Corporate America.

Combined, BlackRock, State Street and Vanguard are the largest owner in 88% of the S&P 500 companies, according to a paper published Tuesday by the American Economic Liberties Project, a group that launched in February taking aim at what it sees as excessive corporate power. For instance, the Big Three hold leading stakes in companies including Apple(AAPL), JPMorgan Chase (JPM) and Pfizer (PFE).

Critics say BlackRock (BLK), Vanguard and State Street (STT)have become too powerful and that the Biden administration and Congress need to rein them in.

“The solution is to go straight at the concentration problem by limiting their market share,” Graham Steele, who wrote the American Economic Liberties Project paper, told CNN Business.

The paper calls for effectively breaking up the Big Three by revamping Dodd-Frank, the 2010 Wall Street reform law.

Steele, a former staffer at the San Francisco Federal Reserve Bank who is now director of the Corporations and Society Initiative at Stanford Graduate School of Business, said he’s hopeful the Biden administration will study potential solutions. But he acknowledged the Big Three will fight back, adding: “They won’t take it lying down.”