Credit downgrades took out about a quarter of the U.S. bond market volume in 2008, suggests a new Fitch Ratings study .

The credit rating agency’s research finds that US$891.9 billion in U.S. corporate bonds in 2008, or 24% of U.S. bond market volume, was affected by downgrades last year, narrowly topping the previous high of 23.4% recorded in 2002 (on US$558.1 billion in downgrades).

“Downgrades, not surprisingly, accelerated significantly in the second half of the year,” said Eric Rosenthal, senior director of Fitch Credit Market Research. “In the fourth quarter alone, downgrades totalled US$391.5 billion, or 10.6% of market volume.”

For the full year, downgrades and upgrades affected 21.7% (US$667.5 billion) and 4% (US$121.8 billion) of investment-grade bonds, respectively, and 34.2% (US$224.4 billion) and 11.4% (US$74.4 billion) of speculative-grade bonds, Fitch reported.

Moreover, bond issuance in the second half of 2008 fell 65.9% compared with the first half of the year and 2008 ended down 30.4% relative to 2007, the firm said.

Fitch also observed that US$502 billion in U.S. corporate bonds is scheduled to mature in 2009, representing 13% of U.S. bond market volume. Financials represent the bulk of maturing bonds at US$389.1 billion. Speculative-grade bond maturities total US$30.6 billion in 2009 and US$107.3 billion through 2011, it said.

“Refinancing risk continues to be an acute concern overall but especially so at the speculative-grade level,” said Mariarosa Verde, managing director of Fitch Credit Market Research. “Mounting pressure on the U.S. high-yield default rate suggests that there will be little relief on this front in 2009.”

www.fitchratings.com