  We point out that annihilation of dark matter in the galactic halo can be
enhanced relative to that in the early universe due to a Breit-Wigner tail, if
the dark matter annihilates through a pole just below the threshold. This
provides a new explanation to the "boost factor" which is suggested by the
recent data of the PAMELA, ATIC and PPB-BETS cosmic-ray experiments.
