  A statistical study of the properties of molecular outflows is performed
based on an up-to-date sample. 391 outflows were identified in published
articles or preprints before February 28, 2003. The parameters of position,
morphology, mass, energy, outflow dynamics and central source luminosity are
presented for each outflow source. Outflow lobe polarity is known for all the
sources, and 84% are found to be bipolar. The sources are divided into low mass
and high mass groups according to either the available bolometric luminosity of
the central source or the outflow mass.Energetic mass ejection may be a common
aspect of the formation of high mass as well as low mass stars. Outflow masses
are correlated strongly with bolometric luminosity of the center sources, which
was obtained for the first time. There are also correlations between the
central source luminosity and the parameters of mechanical luminosity and the
thrust or force necessary to drive the outflow. The results show that flow
mass, momentum and energy depend on the nature of the central source. Despite
their similarity, there are differences between the high mass and low mass
outflows on collimation, flow masses, mass-dynamical time relation and
associated objects such as HH objects and water masers.Sources with
characteristics of collapse or infall comprise 12% of the entire outflow
sample. The spatial distribution of the outflow sources in the Galaxy is
presented and the local occurrence rate is compared with the stellar birth
rate.
