  More reliable constraints on the microlensing optical depth comes from a
better understanding of the Galactic model. Based on well-constrained Galactic
bulge and disk models constructed from survey observations, such as, HST,
2MASS, and SDSS, we calculate the microlensing optical depths toward the
Galactic bulge fields, and compare them with recent results of microlensing
surveys. We test chi^2 statistics of microlensing optical depths expected from
those models, as well as previously proposed models, using two types of data:
optical depth map in (l, b) and averaged optical depth over the Galactic
longitude l as a function of the latitude b. From this analysis, we find that
the Galactic bulge models of 2MASS, Han & Gould (2003), and G2 of Stanek et al.
(1997) show a good agreement with the microlensing optical depth profiles for
all the microlensing observations, compared with E2 of Stanek et al. (1997). We
find, on the other hand, that models involving an SDSS disk model produce
relatively higher chi^2 values. It should be noted that modeled microlensing
optical depths diverge in the low Galactic latitude, |b| < 2 arcdeg. Therefore,
we suggest the microlensing observation toward much closer to central regions
of the Galaxy to further test the proposed Galactic models, if it is more
technically feasible than waiting for large data set of microlensing events.

Astrophysics