The Hipparcos data provide a dramatic increase, qualitatively and quantitatively, of the basic distance information available for many applications. The numbers of stars for which a relative accuracy better than 1, 5, 10 and 20% is now available from Hipparcos data and from ground-based data are given in Table 5.
Table 5: Number of stars per range of relative accuracy of trigonometric
parallaxes
Moreover, the range of spectral types and luminosity classes for which precise parallaxes are available is considerably enlarged, especially towards the upper part of the main sequence and towards the giant branch, where the `clump' is already clearly evident when considering stars with relative accuracy better than 5%. The lower part of the main sequence is populated down to absolute Hp magnitude 14. The ranges of absolute Hp magnitude and B-V covered by Hipparcos observations per range of relative accuracy on trigonometric parallaxes are shown in Table 6.
Table 6: Ranges of absolute Hp magnitude and B-V per range of relative
accuracy of trigonometric parallaxes
The comparison with the last edition of the Catalogue of Nearby Stars (CNS3, Gliese & Jahreiß 1991, stars within 25 pc of the Sun) shows the outstanding improvement expected from the Hipparcos data: in CNS3, which is the best available compilation of nearby stars, there are 851 stars with a relative accuracy of trigonometric parallaxes better than 10% and a measured B-V. Moreover, about a third of the stars appear to be further than 25 pc from Hipparcos observations (Perryman et al. 1995).
The comparison with spectroscopic distances shows the same kind of discrepancy:
from 5610 stars classified V by N. Houk (Michigan Spectral Survey,
Vols 1-3, 
) and estimated at distances
pc, 2384 are shown by Hipparcos to be at distances >80 pc
(Binney et al. 1997).