  We present line and continuum measurements for 9818 SDSS type-I active
galactic nuclei (AGNs) with z le 0.75. The data are used to study the four
dimensional space of black hole mass, normalized accretion rate (Ledd),
metalicity and redshift. The main results are: 1. Ledd is smaller for larger
mass black holes at all redshifts. 2. For a given black hole mass Ledd propto
z^gamma or (1+z)^delta where the slope gamma increases with black hole mass.
The mean slope is similar to the star formation rate slope over the same
redshift interval. 3. The FeII/Hb line ratio is significantly correlated with
Ledd. It also shows a weaker negative dependence on redshift. Combined with the
known dependence of metalicity on accretion rate, we suggest that the FeII/Hb
line ratio is a metalicity indicator. 4. Given the measured accretion rates,
the growth times of most AGNs exceed the age of the universe. This suggests
past episodes of faster growth for all those sources. Combined with the FeII/Hb
result, we conclude that the broad emission lines metalicity goes through
cycles and is not a monotonously decreasing function of redshift. 5. FWHM(OIII)
is a poor proxy of sigma_* especially for high Ledd. 6. We define a group of
narrow line type-I AGNs (NLAGN1s) by their luminosity (or mass) dependent Hb
line width. Such objects have Ledd>0.25 and they comprise 8% of the type-I
population. Other interesting results include negative Baldwin relationships
for EW(Hb) and EW(FeII) and a relative increase of the red part of the Hb line
with luminosity.
