Pension Benefits Other Benefits $ Millions 2000 1999 2000 1999 Change in benefit obligation: Benefit obligation at beginning of year $1,865 $1,907 $(637 $(640 Service cost 50 53 6 8 Interest cost 126 116 46 40  Plan participantsGLYPH<213> contributions 6 7 2 1 Amendments 3 14 -  -  Experience (gain) loss 63 (103) 11 (21)  Benefits paid (122) (119) (37) (31)  Other (36) (10) - - Benefit obligation at end of year $1,955 $1,865 $(665 $(637 Change in plan assets: Fair value of plan assets at beginning of year  $1,922 $1,692 $ - $ - Actual return on plan assets 162 331 - -  Employer contribution 62 20 35 30  Plan participantsGLYPH<213> contributions 6 7 2 1  Benefits paid (122) (119) (37)  (31) Other (35) (9) -  - Fair value of plan assets at end of year $1,995 $1,922 $ - $ - Funded status $ ,40 $ ,57 $(665) $(637)  Unrecognized: Experience (gain) loss (a) (41) (103) 70 55 Prior service cost (b) 43 51 (12) (12) Transition asset (c) (2) (5) -  -  Net amount recognized $ ,40 $ - $(607)  $(594) Amounts recognized in the statement of financial position: Prepaid benefit cost $ ,110 $ ,102 $ - $ - Accrued benefit liability (111) (114) (607) (594)  Intangible asset 38 12 -  -  Accumulated other comprehensive income 3 -  - - Net amount recognized $ ,40 $ - $(607) $(594)  (a) The net deferred (gain) loss resulting from investments, other experience and changes in assumptions. (b) The prior service effect of plan amendments deferred for recognition over remaining service. (c) The balance of the initial difference between assets and obligations deferred for recognition over a 15-year period. 31