  We use symplectic cobordism, and the localization result of Ginzburg,
Guillemin, and Karshon, to find a wall-crossing formula for the signature of
regular symplectic quotients of Hamiltonian torus actions. The formula is
recursive, depending ultimately on fixed point data. In the case of a circle
action, we obtain a formula for the signature of singular quotients as well. We
also show how formulas for the Poincare polynomial and the Euler characteristic
(equivalent to those of Kirwan) can be expressed in the same recursive manner.
