We present line and continuum measurements for 9818 SDSS type-I active galactic nuclei ( AGNs ) with z \leq 0.75 .
The data are used to study the four dimensional space of black hole mass , normalized accretion rate ( L / L _ { Edd } ) , metalicity and redshift .
The main results are : 1 . L / L _ { Edd } is smaller for larger mass black holes at all redshifts .
2 .
For a given black hole mass , L / L _ { Edd } \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/H \beta line ratio is significantly correlated with L / L _ { Edd } .
It also shows a weaker negative dependence on redshift .
Combined with the known dependence of metalicity on accretion rate , we suggest that the FeII/H \beta 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/H \beta result , we conclude that the broad emission lines metalicity goes through cycles and is not a monotonously decreasing function of redshift .
5 .
FWHM ( [ O iii ] \lambda 5007 ) is a poor proxy of \sigma _ { * } especially for high L / L _ { Edd } .
6 .
We define a group of narrow line type-I AGNs ( NLAGN1s ) by their luminosity ( or mass ) dependent H \beta line width .
Such objects have L / L _ { Edd } \geq 0.25 and they comprise 8 % of the type-I population .
Other interesting results include negative Baldwin relationships for EW ( H \beta ) and EW ( FeII ) and a relative increase of the red part of the H \beta line with luminosity .