xpGain = managerLevel * 8 + 10
xpBonus = (topManagerLevel - yourManagerLevel) * 8
xpPerRace = xpGain + xpBonus
What this means
Everyone in a league will gain XP at a rate that matches the top level manager in the league. Due to the dynamic gaps in XP between levels, this means you will level up faster if you are a lower level, but you will not gain XP faster than the top manager. The aim is to bring lower managers up the levels faster, to reach level parity sooner, but not to reach XP parity.