  The NRO/OVRO imaging survey of molecular gas in 20 spiral galaxies is used to
test the theoretical predictions on bar-driven gas transport, bar dissolution,
and bulge evolution. In most galaxies in the survey we find gas condensations
of 10^8-10^9 M_sun within the central kiloparsec, the gas masses being
comparable to those needed to destroy bars in numerical models. We also find a
statistically significant difference in the degree of gas concentration between
barred and unbarred galaxies: molecular gas is more concentrated to the central
kiloparsec in barred systems. The latter result supports the theories of
bar-driven gas transport. Moreover, it constrains the balance between the rate
of gas inflow and that of gas consumption (i.e., star formation, etc.), and
also constrains the timescale of the possible bar dissolution. Namely, gas
inflow rates to the central kiloparsec, averaged over the ages of the bars,
must be larger than the mean rates of gas consumption in the central regions in
order to cause and maintain the higher gas concentrations in barred galaxies.
Also, the timescale for bar dissolution must be longer than that for gas
consumption in the central regions by the same token.
