(b) On January 1, 1981, any beneficiary who was receiving a survivor's monthly benefit on or before January 1, 1971, shall have the benefit then being paid increased by 1% for each full year elapsed from the date the survivor's benefit began. On January 1, 1982, any beneficiary who began receiving a survivor's monthly benefit after January 1, 1971, but before January 1, 1981 shall have the benefit then being paid increased by 1% for each year elapsed from the date the survivor's benefit began. On January 1, 1987, any beneficiary whose monthly survivor's benefit began on or before January 1, 1977, shall have the monthly survivor's benefit increased by $1 for each full year which has elapsed since the date the survivor's benefit began.