  We discuss differences between massive single star and massive close binary
population number synthesis predictions of WR stars. We show that the WC/WN
number ratio as function of metallicity depends significantly on whether or not
binaries are included. Furthermore, the observed WC(+OB)/WN(+OB) number ratio
in the Solar neighborhood seems to indicate that the WR mass loss rates are
lower by another factor two compared to recently proposed clumping corrected
formalisms. We then demonstrate that the observed lower luminosity distribution
of single WN stars can be explained in a satisfactory way by massive single
star evolutionary computations where the red supergiant phase is calculated
using a stellar wind mass loss rate formalism that is based on recent
observations.
