  Gamma-ray Burst (GRB) collimation has been inferred with the observations of
achromatic steepening in GRB light curves, known as jet breaks. Identifying a
jet break from a GRB afterglow lightcurve allows a measurement of the jet
opening angle and true energetics of GRBs. In this paper, we reinvestigate this
problem using a large sample of GRBs that have an optical jet break which is
consistent with being achromatic in the X-ray band. Our sample includes 99 GRBs
from February 1997 to March 2015 that have optical and, for Swift GRBs, X-ray
lightcurves that are consistent with the jet break interpretation. Out of 99
GRBs we have studied, 55 GRBs are found to have temporal and spectral behaviors
both before and after the break consistent with the theoretical predictions of
the jet break models, respectively. These include 53 long/soft (Type II) and 2
short/hard (Type I) GRBs. Only 1 GRB is classified as the candidate of a jet
break with energy injection. Another 41 and 3 GRBs are classified as the
candidates with the lower and upper limits of the jet break time, respectively.
The typical beaming correction factor $f_b^{-1} \sim 1000$ for Type II GRBs,
suggesting an even higher total GRB event rate density in the universe. Both
isotropic and jet-corrected energies have a wide span in their distributions.
We also investigate several empirical correlations (Amati, Frail, Ghirlanda and
Liang-Zhang) previously discussed in the literature. We find that in general
most of these relations are less tight than before. The existence of early jet
breaks and hence small opening angle jets, which were detected in the {\em
Swfit era}, is most likely the source of scatter. If one limits the sample to
jet breaks later than $10^4$ s, the Liang-Zhang relation remains tight and the
Ghirlanda relation still exists. These relations are derived from Type II GRBs,
and Type I GRBs usually deviate from them.
