With each level of this perk, additional +5% bonus is given whenever Experience Points are earned.
Most useful at the beginning, this perk ceases to provide gain in XP once the character reaches the level cap (Fallout 1 = 21; Fallout 2 and Fallout Tactics = 99).
If taken at levels 3, 6 and 9, the amount of experience received from it allows to gain "extra" level once the player would normally reach level 17 (17700 XP compared to 17000 XP difference between levels 17 and 18).
The perk has no effect in Fallout Tactics. [verified]