81. To determine the annual salary for the years following the year in which the pensioner retired, the salary is adjusted annually and at the intervals prescribed under section 119 of the Act respecting the Québec Pension Plan (chapter R-9), according to the rate of increase of the Pension Index determined by the said Act. The first adjustment is made proportionately to the number of days for which the pensioner received benefits in the year he retired in relation to the total number of days in that year.