Picture this scenario: Low interest rates and easy credit lead to borrowers taking out lots of loans, including high-risk loans. Financial institutions bundle those loans into new investment products, which are snapped up by the financial sector.

That describes both the subprime mortgage market that sparked the 2008 financial crisis and today’s corporate debt.

Corporate debt in the United States has risen to a near-record high, almost 50% of the gross domestic product. And in September, corporations sold $434 billion worth of bonds globally — the most ever.

That’s spurred concerns among some economists that the corporate debt binge is unsustainable and could lead to a future crisis.