Under normal circumstances, the fund will invest primarily in instruments that are rated, at the time of purchase, below investment grade (below BBB- by Standard & Poor's Rating Services ("S&P") or Fitch, Inc. ("Fitch") or below Baa3 by Moody's Investors Service, Inc. ("Moody's")), or comparably rated by another nationally recognized statistical rating organization ("NRSRO"), or unrated but determined by Artisan Partners to be of comparable quality.