  We update the values of the eta-eta' mixing angle and of the eta' gluonium
content by fitting our measurement R_phi = BR(phi to eta' gamma)/ BR(phi to eta
gamma) together with several vector meson radiative decays to pseudoscalars (V
to P gamma), pseudoscalar mesons radiative decays to vectors (P to V gamma) and
the eta' to gamma gamma, pi^0 to gamma gamma widths. From the fit we extract a
gluonium fraction of Z^2_G = 0.12 +- 0.04, the pseudoscalar mixing angle psi_P
= (40.4 +- 0.6) degree and the phi-omega mixing angle psi_V = (3.32 +- 0.09)
degree. Z^2_G and psi_P are fairly consistent with those previously published.
We also evaluate the impact on the eta' gluonium content determination of
future experimental improvements of the eta' branching ratios and decay width.
