The set of active investors plus the set of passive investors is the set of all market participants. If the passive investors all earn the market average, then

The set of active investors plus the set of passive investors is the set of all market participants. If the passive investors all earn the market average, then the average earnings of active investors, before fees, must also be equal to the market average. Since passive investors pay less fees and active investors, the average earnings of an active investors, after fees, must always be less than that of the passive investor.