The fund normally invests at least 80 percent of its assets in debt securities rated below investment grade (also referred to as high yield debt securities or junk bonds). It uses the ICE BofA BB-B US High Yield Constrained Index as a guide in structuring the fund and selecting its investments as it relates to credit quality distribution and risk characteristics. The fund normally invests primarily in securities rated BB or B by S&P, Ba or B by Moodys, comparably rated by at least one nationally recognized credit rating agency, or, if unrated, considered by FMRC to be of comparable quality.