  The distributions of the stellar metallicities of K giant stars in several
fields of the Galactic bulge, taken from the literature are compared with a
simple model of star formation and chemical evolution. Our model assumes a
Schmidt law of star formation and is described by only a few parameters that
control the infall and outflow of gas and the star formation efficiency. We
find that very short infall timescales are needed, with durations of infall and
star formation greater than 1 Gyr being ruled out at the 90% confidence level.
The metallicity distributions are compatible with an important amount of gas
and metals being ejected in outflows, although a detailed quantification of the
ejected gas fraction is strongly dependent on a precise determination of the
absolute stellar metallities. The recent bulge data from Zoccali et al. are
also analyzed, and the subsample with subsolar metallicities still rules out
infall timescales around 1 Gyr at the 90% confidence level. Hence, the short
timescales we derive based on the observed distribution of metallicities are
robust and should be taken as stringent constraints on bulge formation models.
