Further decides that, during a period of three years from 1 January 1974, the pension adjustment index used for purposes of adjustment of benefits shall be replaced by a revised pension adjustment ~ndex, which shall be calculated for 1 January 197 4 m the manner indicated in paragraph 16 of the report of the Advisory Committee on Administrative _and Budgetary Questions16 and shall thereafter be ad1usted and operated in accordance with the recommendations in section B of annex V to the report of the United Nations Joint Staff Pension Board,14 subject to such changes as may result from the introduction of the revised index on 1 January 1974;