  We revisit the observed frequencies of Carbon-Enhanced Metal-Poor (CEMP)
stars as a function of the metallicity in the Galaxy, using data from the
literature with available high-resolution spectroscopy. Our analysis excludes
stars exhibiting clear over-abundances of neutron-capture elements, and takes
into account the expected depletion of surface carbon abundance that occurs due
to CN processing on the upper red-giant branch. This allows for the recovery of
the initial carbon abundance of these stars, and thus for an accurate
assessment of the frequencies of carbon-enhanced stars. The correction
procedure we develope is based on stellar-evolution models, and depends on the
surface gravity, log g, of a given star. Our analysis indicates that, for stars
with [Fe/H]<=-2.0, 20% exhibit [C/Fe]>=+0.7. This fraction increases to 43% for
[Fe/H]<=-3.0 and 81% for [Fe/H]<=-4.0, which is higher than have been
previously inferred without taking the carbon-abundance correction into
account. These CEMP-star frequencies provide important inputs for Galactic and
stellar chemical-evolution models, as they constrain the evolution of carbon at
early times and the possible formation channels for the CEMP-no stars. We also
have developed a public online tool with which carbon corrections using our
procedure can be easily obtained.
