  The zero temperature Hall constant R_H, described by reactive
(nondissipative) conductivities, is analyzed within linear response theory. It
is found that in a certain limit, R_H is directly related to the density
dependence of the Drude weight implying a simple picture for the change of sign
of charge carriers in the vicinity of a Mott-Hubbard transition. This novel
formulation is applied to the calculation of R_H in quasi-one dimensional and
ladder prototype interacting electron systems.
