With pension plans all but in the past and the Social Security trust fund staring down a 75-year deficit, 401(k) plans are the only sure bet for younger Americans who hope to retire one day.

Today, more Americans are saving for retirement than ever before, and they’re using 401(k)s to do so — which means that all of that wealth has accumulated among Wall Street’s four largest asset managers: BlackRock, Vanguard Group, Fidelity Investments and State Street Global Advisors, CNN Business reported.

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BlackRock boasts $9 trillion under management, Vanguard $7.2 trillion, Fidelity $4.2 trillion and State Street $3.5 trillion: Together, the four companies are in charge of assets worth 65% of the total value of the shares in the S&P 500, per the outlet.

Although the average 401(k) plan tumbled more than 20% in 2022, Americans continue to contribute at a steady rate — with a recent study finding that workers expect to need $1.25 million for a comfortable retirement, CBS News reported.

Of course, shareholders have the right to vote on happenings in company operations, but proxy voting means huge asset managers can do so on behalf of their clients, effectively impacting a company’s actions and direction themselves.

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Some say that such concentrated ownership could wreak havoc.

Asset managers possess “significant influence over company practices” and vote on resolutions that could change the course of our planet, shareholder advocacy group ShareAction wrote in a recent report, and Harvard Law professor Einer Elhauge called the imbalance the “greatest anticompetitive threat of our time,” per CNN.