  It is shown that in the instanton approximation the rate of creation of black
holes is always enhanced by a factor of the exponential of the black hole
entropy relative to the rate of creation of compact matter distributions
(stars). This result holds for any generally covariant theory of gravitational
and matter fields that can be expressed in Hamiltonian form. It generalizes the
result obtained previously for the pair creation of magnetically charged black
holes by a magnetic field in Einstein--Maxwell theory. The particular example
of pair creation of electrically charged black holes by an electric field in
Einstein--Maxwell theory is discussed in detail.
