Cumulative fraction of the energy output of the known Galactic pulsar population with ages < 10⁷ yr (Manchester et al. 2005) created using the instantaneous energy output into electrons E_e as well as the energy output integrated up to 10⁴ and 10⁵ yr electron lifetimes. For comparison purposes, we show the cumulative γ-ray luminosity at 1 TeV from a generic PWN model as a function of system age, both for a constant magnetic field and a magnetic field evolving in time. The cumulative fraction of pulsars indicates that the energy output into electrons and γ-ray luminosity is dominated by a small fraction of young, energetic pulsars.