The role of bars in driving secular evolution of galaxies is still
highly debated. Studies on the fraction of barred galaxies in the
local universe, their evolution with redshift, and their role in
building bulges and triggering AGN have not yielded consistent
results. Using a sample of ~30,000 visually and quantitatively
classified galaxies with spectroscopic redshifts from SDSS and
zCOSMOS, I will present results characterizing the role of bars in the
build-up of galaxies. I will contrast this to the role of
merger-induced gas inflow processes and time permitting, the role of
AGN.