Statistics of 2341 detected OH masers in the database. The upper panels show in a) the distribution in Galactic longitudes; and in b) in Galactic latitudes. The lower panels show in c) the distribution on the sky in Galactic coordinates; and in d) the range of Galactic latitudes for given expansion velocities. This last plot uses velocity information from 1967 stars and is truncated at 35 km s^-1 for display purposes, excluding 15 sources with v_exp = 35−80 km s^-1.