. it is an estimate of the potential value depreciation over a one year horizon commensurate with solvency expectations of an institution rated single-a by the credit rating agencies . given the illiquid nature of many of these types of investments , it can be a challenge to determine their fair values . see note 7 fair value in the notes to consolidated financial statements in item 8 of this report for additional information . various pnc business units manage our equity and other investment activities