Under normal conditions, the Fund invests at least 80 percent of its net assets, plus the amount of any borrowings for investment purposes, in debt obligations or investments that provide exposure to such debt obligations. The Fund may invest up to 25 percent of its net assets in debt obligations which, at the time of purchase, are rated by a nationally recognized statistical rating organization as below investment grade (sometimes called junk bonds or high yield bonds) or, if unrated, are issued by obligors which Thornburg determines to have comparable below investment grade obligations outstanding or to be comparable to obligors with outstanding below investment grade obligations.