Total debt issued by non-financial U.S. corporations at the end of 2017 was about $6.1 trillion, its highest level since the Fed began tracking the data in 1947. Corporate debt has grown on a year-over-year basis every quarter since June 2005 and averaged slightly more than 6.4% since the end of the financial crisis. For the most part, cash flows have kept pace with the added leverage. December 2017's dramatic decline in cash flows relative to debt is an outlier, likely related to the GOP tax bill. September's data were included for perspective as cash flow numbers typically dip in December on income-tax payments.
The ratio of corporate debt to cash flow ticked up in 2017 relative to the previous two years, with corporate M&A activity and the likelihood of higher future lending costs looming. Relative to the market value of corporate equity, non-financial corporate debt is about one-third of the dollar value; it was about 76% at the peak of the crisis, and just less than half at the end of 2011.