  We present a novel method to measure the accretion rate of radio emitting
X-ray binaries (XRBs) and active galactic nuclei (AGN) independently of the
X-ray luminosity. The radio emission of the jet is used as a tracer for the
accretion rate and is normalised using sources of known accretion rates: island
state neutron stars and efficiently radiating black holes close to a state
transition. We show that the radio power in black holes and neutron stars is
comparable for a given mass accretion rate and verify empirically the assumed
analytic scaling of the radio luminosity with accretion rate. As our accretion
measure is independent of the X-ray luminosities, we can search for radiatively
inefficient accretion in black holes by comparing the X-ray luminosities with
the accretion rate in XRBs and AGN. While the X-ray luminosity of efficiently
radiating objects scales linearly with accretion rate, the scaling of hard
state black holes is quadratical, in agreement with theoretical models. We show
that the turnover from the inefficient quadratic scaling to the linear scaling
has to occur at accretion rates of 1-10 % Eddington both in XRBs and AGN. The
comparison of both accretion states supports the idea that in a black hole in
the hard state some accretion power is advected into the black hole while the
jet power exceeds the X-ray luminosity: these are therefore jet-dominated
advective systems.

Astrophysics