AMERICA’s companies have been powering ahead for years. Amid growing profits, the recession that began in 2007 seems an increasingly distant memory. Yet the situation has a dark side: companies have binged on debt. For now, as the good times have coincided with a period of record-low interest rates, markets have been untroubled. But a shock could put corporate America into trouble.

No matter how it is measured, the debt load looks worrying. When calculated as a percentage of GDP, the total debt of America’s non-financial corporations reached 73.3% in the second quarter of 2017 (the latest available data). This is a record high. Measured against earnings before interest, tax, depreciation and amortisation (EBITDA), the net debt of non-financial companies in the S&P500 hit a ratio of 1.5 at of the end of 2016, a level not seen since 2003. And it remained nearly as high in 2017 (see chart).

To be sure, things are less worrying than they were before the financial crisis. According to a recent analysis by S&P Global Ratings, a ratings agency, for example, debt is now more evenly distributed. Only 27% of American firms in 2017 were highly levered (defined as a debt-to-earnings ratio higher than five), down from 42% of firms in 2007, meaning that fewer firms are immediately at risk.

The use of the extra debt was also somewhat different. Bob Michele of J.P. Morgan reckons that in recent years much of it was used by companies to finance share buy-backs, essentially for purposes of balance-sheet management (rather than, say, big expansions or acquisitions).

Even so, certain industries look particularly vulnerable under their debt loads. David Tesher of S&P Global Ratings says that retail is the sector in America most at risk. Such companies accumulated high levels of debt after more than a decade of private-equity-sponsored activity. They must also cope with tough competition from e-commerce. Around 50 American retailers filed for bankruptcy in 2017 alone, many due to the debt piled on by their private-equity owners. The most prominent example is Toys R Us, which was acquired by a consortium of private-equity firms in 2005. In the case of Payless ShoeSource, a retailer that also went bankrupt last year, creditors argued in court filings that its private-equity owners should share the blame for its collapse; after much argument, the owners agreed to put more than $20m back into the company.