  We have used main-sequence fitting to calibrate the distances to the globular
clusters NGC 6397, M5, NGC 288, M71 and 47 Tucanae, matching the cluster
photometry against data for subdwarfs with precise Hipparcos parallax
measurements and accurate abundance determinations. Both the cluster and
subdwarf abundance scales are tied to high-resolution spectroscopic analyses.
The distance moduli that we derive for the five clusters are 12.24, 14.52,
15.00, 13.19 and 13.59 magnitudes, with uncertainties of +/- 0.15 magnitudes.
As in previous analyses by Reid (1997) and Gratton et al (1997), those
distances are higher than those derived in pre-Hipparcos investigations.
  The calibrated cluster colour-magnitude diagrams provide fiducial sequences
in the (M(V), (B-V)) plane, outlining the distribution expected for stars of a
particular abundance. We have combined the photometric data for NGC 6397
([Fe/H]=-1.82 dex), M5 (-1.10 dex) and 47 Tucanae (-0.70 dex) with the mean
colour-magnitude relation delineated by nearby FGK dwarfs to define a reference
grid in the (M(V), (B-V)) plane, and we have matched this grid against data for
stars drawn from the Lowell proper motion survey, with both Hipparcos
astrometry and abundance determinations by Carney et al (1994). Limiting the
comparison to non-binaries, there are significantly fewer subluminous stars
than expected given the spectroscopic metallicity distribution. Inverting the
analysis, this implies a reduction by a factor of three in the proportion of
stars contributing to the metal-poor ([Fe/H] < -0.4) tail of the Galactic disk.
We discuss the implications of these results.
