Spectrophotometry of two complete samples of flat-spectrum radio quasars show that for these objects there is a strong correlation between the equivalent width of the C IV 1550 A emission line and the luminosity of the underlying continuum. Assuming Friedmann cosmologies, the scatter in this correlation is a minimum for Q(O) approximately unity. Alternatively, luminosity evolution can be invoked to give compact distributions for Q(O) approximately zero models. A sample of Seyfert galaxies observed with IUE shows that despite some dispersion the average equivalent width of C IV 1550 A in Seyfert galaxies is independent of the underlying continuum luminosity. New redshifts are given for four quasars.