  The susceptibilities of the real and imaginary parts, as well as of the
modulus of the Polyakov loop, are computed in SU(3) lattice gauge theory. We
show that the ratios of these susceptibilities are excellent probes of the
deconfinement transition, independent of the renormalization of the Polyakov
loop and only weakly dependent on the system size. The ratios are almost
temperature independent above and below the transition and exhibit a
discontinuity at the transition temperature. This characteristic behavior can
be understood in terms of the global Z(3) symmetry of the Yang-Mills Lagrangian
and the general properties of the Polyakov loop probability distribution.
