  Deep redshift surveys of the universe provide the basic ingredients to
compute the probability distribution function (PDF) of galaxy fluctuations and
to constrain its evolution with cosmic time. When this statistic is combined
with analytical CDM predictions for the PDF of mass, useful insights into the
biasing function relating mass and galaxy distributions can be obtained. In
this paper, we focus on two issues: the shape of the biasing function and its
evolution with redshift. We constrain these quantities by using a preliminary
sample of galaxies spectroscopically surveyed by the Vimos-VLT Deep Survey in a
deep cone 0.4<z<1.5 covering 0.4x0.4 sq. deg. We show that the ratio between
the amplitude of galaxy fluctuations and the underlying mass fluctuations
declines with cosmic time, and that its evolution rate is a function of
redshift: biasing evolution is marginal up to z~0.8 and more pronounced for z >
0.8.
