  A new method to determine the bias parameter of galaxies relative to matter
is suggested. The method is based on the assumption that gravity is the
dominating force which determines the formation of the structure in the
Universe. Due to gravitational instability the galaxy formation is a threshold
process: in low-density environments galaxies do not form and matter remains in
primordial form. We investigate the influence of the presence of void and
clustered populations to the power spectrum of matter and galaxies. The power
spectrum of galaxies is similar to the power spectrum of matter; the fraction
of total matter in the clustered population determines the difference between
amplitudes of fluctuations of matter and galaxies, i.e. the bias factor. To
determine the fraction of matter in voids and clustered population we perform
numerical simulations. The fraction of matter in galaxies at the present epoch
is found using a calibration through the sigma_8 parameter.
