Supersymmetric terms in the effective action of N=2 supergravity in four
dimensions are generically classified into chiral-superspace integrals and
full-superspace integrals. For a theory of N=2 vector multiplets coupled to
supergravity, a special class of couplings is given by chiral-superspace
integrals that are governed by a holomorphic prepotential function. The quantum
entropy of BPS black holes in such theories depends on the prepotential
according to a known integral formula. We show, using techniques of
localization, that a large class of full-superspace integrals in the effective
action of N=2 supergravity do not contribute to the quantum entropy of BPS
black holes at any level in the derivative expansion. Our work extends similar
results for semi-classical supersymmetric black hole entropy, and goes towards
providing an explanation of why the prepotential terms capture the exact
microscopic quantum black hole entropy.Comment: 22 page