  The Josephson sum rule relates the superfluid density to the condensate order
parameter, via the infrared residue of the single-particle Green's function. We
establish an effective Josephson relation for disordered condensates valid upon
ensemble averaging. This relation has the merit to show explicitly how
superfluidity links to the coherent density, i.e., the density of particles
with zero momentum. Detailed agreement is reached with perturbation theory for
weak disorder.
