  We have developed a model-independent analytical method for debiasing the
four-dimensional (a,e,i,H) distribution obtained in any asteroid observation
program and have applied the technique to results obtained with the 0.9m
Spacewatch Telescope. From 1992 to 1995 Spacewatch observed ~3740 deg^2 near
the ecliptic and made observations of more than 60,000 asteroids to a limiting
magnitude of V~21. The debiased semi-major axis and inclination distributions
of Main Belt asteroids in this sample with 11.5<= H <16 match the distributions
of the known asteroids with H <11.5. The absolute magnitude distribution was
studied in the range 8< H <17.5. We have found that the set of known asteroids
is complete to about absolute magnitudes 12.75, 12.25 and 11.25 in the inner,
middle and outer regions of the belt respectively. The number distribution as a
function of absolute magnitude cannot be represented by a single power-law
(10^{alpha H}) in any region. We were able to define broad ranges in H in each
part of the belt where alpha was nearly constant. Within these ranges of H the
slope does not correspond to the value of 0.5 expected for an equilibrium
cascade in self-similar collisions (Dohnanyi, 1971). The value of alpha varies
with absolute magnitude and shows a `kink' in all regions of the belt for H~13.
This absolute magnitude corresponds to a diameter ranging from about 8.5 to
12.5 km depending on the albedo or region of the belt.
