The rate evolution of subluminous Type Ia Supernovae is presented using
data from the Supernova Legacy Survey. This sub-sample represents the
faint and rapidly-declining light-curves of the observed supernova Ia
(SN Ia) population here defined by low stretch values (s<0.8). Up to
redshift z=0.6, we find 18 photometrically-identified subluminous SNe
Ia, of which six have spectroscopic redshift (and three are
spectroscopically-confirmed SNe Ia). The evolution of the subluminous
volumetric rate is constant or slightly decreasing with redshift, in
contrast to the increasing SN Ia rate found for the normal stretch
population, although a rising behaviour is not conclusively ruled out.
The subluminous sample is mainly found in early-type galaxies with
little or no star formation, so that the rate evolution is consistent
with a galactic mass dependent behavior: $r(z)=A\times M_g$, with
$A=(1.1\pm0.3)\times10^{-14}$ SNe per year and solar mass.
