Most of these ETFs invest in bonds rated below investment grade by credit rating agencies, which is below ‘BBB-' by Standard & Poor's or Fitch, or below ‘Baa3' from Moody's. Investors who are interested in higher current income and have a high tolerance for risk are best suited for this particular category. High yield bonds may fluctuate in value greatly, depending on if the economic situation of the issuer is improving or worsening. We would view this category as only for aggressive investors.