Bridgewater, the most successful hedge fund, released a report that said corporate profit margins have increased rapidly in the past 20 years because of declining labor shares.

In industries where unionization decreased, wages also fell. Union members went from being about one-fourth of the workforce to just over 10% of it today.

" We are in the midst of a populist backlash," the report said.

Corporations may have hit peak profits over the past 25 years — but workers did not see that in their wages.

Bridgewater Associates, the largest hedge fund, is run by the billionaire Ray Dalio. It recently released a report on how US corporations have seen profit margins soar over the past two decades.

In what Bridgewater called "the most pro-corporate environment in history," the past 20 years have seen corporate taxes and labor bargaining power fall as globalization and automation have increased.

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The biggest driving factor behind soaring profits, Bridgewater reported, is the decline in the share of profits that workers receive. The decline in unionization among US workers, and to a lesser extent the advance of technology and outsourcing of jobs, is driving worker wages down.

In companies that had union membership decline, wages fell at a greater level than in sectors where union membership remained intact. Transportation, manufacturing, and construction jobs were hit the hardest: These three industries had union membership decline by as much as 9%, while national wages grew only about 1.7 to 2.5% since 2000. Jobs in the financial sector, meanwhile, had the most growth in union membership since 2000 and saw wages increase by nearly 3%.

As a whole, union members went from being about one-fourth of the workforce to just over 10% of it today.

"While changes in union activity have been smaller in recent years, even small moves toward or away from unionization can be linked to changes in how much firms pay their employees," the report said.

Earlier this year, Dalio called the current levels of income inequality a "national emergency," warning that these conditions will ultimately weaken the US economy and reduce the country's strength relative to other global leaders.

The solutions Dalio offered to fix income inequality include increasing taxes on the wealthy and strengthening coordination between the White House, the Federal Reserve, and Congress.

The call to raise taxes on the ultra-rich is becoming more mainstream. Rep. Alexandria Ocasio-Cortez recently proposed a marginal tax rate of 70% on income of more than $10 million, bringing it back to levels that were last seen in the 1970s. Two Democratic presidential candidates' plans to increase taxes on the rich are polling well among Americans.

Bridgewater said the margin growth may not persist because more people are recognizing that the power of big companies has come at the expense of worker pay. The firm predicted more government regulation of corporations and said survey data suggests people feel growing animosity toward globalization and the sweeping power of companies.

"We are in the midst of a populist backlash against rising inequality and increasingly seeing a move toward more protectionism," the report said.