After PG&E, keep an eye on corporate debt

Both Moody's and S&P Global downgraded PG&E from investment grade to junk this week, meaning the California utility is likely in for some major upheaval.

Why it matters: PG&E's problems are unique, but the company's recent trouble highlights a growing risk in the credit market for companies that technically have investment grade debt, but are teetering on the brink of junk status. A weakening economic and credit cycle could spark a slew of downgrades, with half of investment-grade debt in the lowest-rated rank.

• Driving the news: PG&E could face up to $30 billion in liability costs related to fires California wildfires. It has about $50 billion in outstanding liabilities vs. $71 billion in assets, and its shares have lost more than two-thirds of their market value since the most recent fires in Nov.

The number of companies with debt just one level above junk has swelled 247% since the end of 2007, faster than the 190% increase for the overall credit market. But so far, only 7% of these companies has been downgraded, according to Fitch Ratings.

• A downgrade would make it pricier for companies to tap into capital markets, which some rely on for growth and others just to keep things running. A downgrade to junk can also force fund managers who only hold investment grade debt to sell, and high-yield managers might not be interested until the price falls further.

The bottom line: Corporations have ratcheted up their debt load to the tune of $9 trillion since the financial crisis, thanks to easy money and a long period of low interest rates. S&P Global analysts noted recently that the booming credit cycle is "in its later stages."