It may come as a surprise that a substantial portion of America’s economy is worker- and union-owned — technically. Private sector and public sector union members’ pension funds collectively manage roughly $8 trillion in worker savings. That’s nearly 15 percent of Wall Street. But those funds — comprising the monthly contributions of millions of workers and enabled (in part) by union organizing and collective bargaining — are often invested in (and by) firms that harm workers.

The labor movement has long tried to harness the economic power tied up in its vast stores of capital: labor’s “last best weapon.” Proposals abound: divesting from nonunion companies, intensifying pro-labor shareholder activism, and acquiring bigger stakes in union-driven or worker-friendly asset managers (like the AFL-CIO Housing Investment Trust) that finance union-labor projects. But none have been attempted at the scale needed to reap their promised rewards. And all push up against the narrow definition of “fiduciary” that prevents pension fund trustees from considering much more than their fund’s rate of return.

Still, none of that should stop the labor movement from being ambitious and imaginative. It’s time to dust off an often-overlooked chapter of not-too-distant labor history, “one of the most promising roads not taken.” That’s the Meidner Plan, a proposal to put Sweden on a path to achieving real workplace democracy through collective worker control over the country’s largest corporations. The plan has a simple lesson for those interested in mobilizing labor’s capital: ownership matters.