The number of junk-rated companies that defaulted on debt repayments almost doubled in 2015 and the picture may worsen further this year, according to Moody’s Investors Service.

There were 108 speculative-grade defaults worldwide last year, up from 55 the previous year, Moody’s said in a report on Thursday, citing its criteria. The default rate climbed to 3.4 percent of issuers for the 12 months ended December, it said.

A slump in commodities and slowing economic growth in China, the world’s biggest consumer of raw materials, pounded sub-investment grade companies particularly in the metals, mining, oil and gas industries. Chesapeake Energy Corp., California Resources Corp. and Offshore Group Investment Ltd. were among companies that Moody’s said defaulted on debt obligations last year.

The increasing cost of borrowing will add to continued economic woes and push the default rate to 3.9 percent by the end of 2016, according to the report. The average yield on corporate junk bonds worldwide reached 8.85 percent on Wednesday, the highest in four years, based on Bank of America Merrill Lynch index data.

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