Investor appetite in the U.S. for noninvestment-grade European debt is at a record high, with a 67% increase this year in high-yield products compared with 2012. "This is a lot to do with a lot of companies refinancing debt," said Bryn Jones, head of fixed-income research at Rathbones. "Banks aren't lending as much, so they're coming to the bond market. They're using this window of opportunity. When the economy starts doing well, spreads are going to be tight."