The power of the jets and radio activity of quasars appears to be determine
d by the spin parameter of the black holes in the host galaxies. In this pa
per, the space number density of radio-loud quasars in cold dark matter cos
mologies with biasing factors b(f) = 1 and b(f) = 1.5 is computed, assuming
that radio-loud quasars are created when two galaxies merge, forming a rap
idly spinning black hole in the center. Our results are consistent with the
observational data if quasars have lifetimes of similar to 10(7)-10(8) yr.
Our present model supports the idea that some of the luminous radio galaxi
es may not contain a quasar in their centers.