  For the sample from Ge et al. of 87 low-$z$ Palomar--Green (PG) quasi-stellar
objects (QSOs) and 130 high-$z$ QSOs ($0<z<5$) with $\hb$-based single-epoch
supermassive black hole (SMBH) masses, we performed a uniform decomposition of
the \civ\ $\lambda$1549 broad-line profile. Based on the rest frame defined by
the \oiii $\lambda$5007 narrow emission line, a medium-strong positive
correlation is found between the \civ\ blueshift and the luminosity at 5100\AA\
or the Eddington ratio \leddR. A medium-strong negative relationship is found
between the \civ\ blueshift and \civ\ equivalent width. These results support
the postulation where the radiation pressure may be the driver of \civ\
blueshift. There is a medium strong correlation between the mass ratio of
\civ-based to $\hb$-based \mbh and the \civ\ blueshift, which indicates that
the bias for \civ-based \mbh is affected by the \civ\ profile.
