I report the current status on the determinations of the baryon fractions and dynamical/lensing masses of galaxy clusters as well as the \sigma - T relationship , making use of all the published data in literature which include 304 measurements for baryon fractions , 320/21 data points for masses of intracluster gas/cluster galaxies , ( 152+228 ) /72 data points for cluster masses derived from X-ray emitting gas/optical galaxies based on the hydrostatic equilibrium hypothesis , 46/33 measurements for the projected cluster masses obtained from strong/weak lensing .
A straightforward statistical analysis yields the following features : ( 1 ) The cluster baryon fraction indeed shows an increasing tendency to reach a value of \sim 30 \% at large cluster radius .
( 2 ) The dynamical cluster masses are in fairly good agreement with the masses determined by weak lensing technique ; ( 3 ) The cluster masses provided by strong lensing and other methods are essentially consistent within a factor of \sim 2 .
( 4 ) The cluster \sigma - T relationship is in concordance with the scenario that overall galaxy clusters are the well relaxed dynamical systems .
These results are strongly suggestive of a low-mass density universe ( \Omega _ { m } < 0.3 ) , in which the fraction of baryonic matter ( \sim 30 \% ) is not very small !