  We present stellar parameters and metallicities, obtained from a detailed
spectroscopic analysis, for a large sample of 98 stars known to be orbited by
planetary mass companions (almost all known targets), as well as for a
volume-limited sample of 41 stars not known to host any planet. For most of the
stars the stellar parameters are revised versions of the ones presented in our
previous works. However, we also present parameters for 18 stars with planets
not previously published, and a compilation of stellar parameters for the
remaining 4 planet-hosts for which we could not obtain a spectrum. A comparison
of our stellar parameters with values of Teff, log(g), and [Fe/H] available in
the literature shows a remarkable agreement. The derived [Fe/H] values are then
used to confirm the previously known result that planets are more prevalent
around metal-rich stars. Furthermore, we confirm that the frequency of planets
is a strongly rising function of the stellar metallicity, at least for stars
with [Fe/H]>0. While only about 3% of the solar metallicity stars in the
CORALIE planet search sample were found to be orbited by a planet, this number
increases to more than 25% for stars with [Fe/H] above +0.3. Curiously, our
results also suggest that these percentages might remain relatively constant
for values of [Fe/H] lower than about solar, increasing then linearly with the
mass fraction of heavy elements. These results are discussed in the context of
the theories of planetary formation.
