  Starting from the Kubo formula, we expand the Hall conductivity using a
cumulant approach which converges quickly at high temperatures (k_BT > energy
differences of initial and final scattering states) and can be extended to low
temperatures. The theory can deal with the sign, the ordinary and the anomalous
contributions to the Hall effect. When applied to include the spin-orbit
interaction to first order, we recover what is essentially the
Karplus-Luttinger result for the anomalous Hall effect. Contact is made to the
Chazalviel and Nozieres-Lewiner formulae. A side-jump type formula is obtained
by using an exact application of linear response. We show that there exists an
exact rigid Hall current which is not a Fermi level property. We introduce a
relationship between mass and diffusivity which allows us to generalize the
theory to strong disorder and even introduce a mobility edge. The formalism
provides a systematic and practical way of analyzing both ordinary and
anomalous contributions to the Hall conduction including the changes of sign,
and in the presence of serious disorder. As a byproduct of the method, we show
that the anomalous Hall coefficient can vary with resistance to the power n,
with 1 <= n <= 2 depending on the degree of coherence.
