Spreads of Corporate Bond Yields over Comparable Off-the-Run Treasury Yields, 1997-2006. Chart of spreads of corporate bond yields over comparable off-the-run Treasury yields, 1997 to 2006. For details, refer to the text immediately preceding this chart. Note: The data are daily and extend through February 8, 2006. The high-yield index is compared with the five-year Treasury yield, and the BBB and AA indexes are compared with the ten-year Treasury yield. Source: Merrill Lynch AA and BBB indexes and Merrill Lynch Master II high-yield index.