Source : Webster's Revised Unabridged Dictionary (1913)

Proportionally \Pro*por"tion*al*ly\, adv.
   In proportion; in due degree; adapted relatively; as, all
   parts of the building are proportionally large. --Sir I.
   Newton.

Source : WordNet®

proportionally
     adv : to a proportionate degree; "your salary will rise
           proportionately to your workload" [syn: {proportionately}]
           [ant: {disproportionately}]