(Bloomberg) -- BlackRock Inc. says that the scale of restructuring needs globally could exceed the previous peak that followed the 2008 global financial crisis.

“One big reason is the significant growth in sub-investment grade debt,” the company’s research arm, BlackRock Investment Institute, said in a note dated Oct. 19. The amount of outstanding debt with ratings below investment grade, including loans and private credit, has more than doubled to $5.3 trillion since 2007, according to the asset manager.

As the overall cost of borrowing fell, companies loaded up on debt. This has left many vulnerable as their revenues came under pressure from Covid-19 related disruptions.

BlackRock isn’t the only one warning of the risks of company failures. Despite low rates, U.S. corporate bankruptcies posted their worst third quarter ever.

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While supportive fiscal and monetary policies have helped companies raise capital and lower borrowing costs, “not all borrowers have benefited equally” and smaller firms have lacked access to the public markets, BlackRock said in the note.

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