The percentage of U.S. retailers that have earned high-risk CCC ratings has doubled since January, according to a new report by S&P.

The S&P ranks a company’s credit ratings on a scale of AAA-D. Higher ratings mean that the company is likely to meet its financial commitments, while lower ratings indicate the opposite. A CCC rating is on the lower end of the scale.

Eighteen percent of U.S. retail ratings are now in the CCC range, which is likely due to online competition and changing shopping patterns.