The age and abundance structure of the stellar populations in the
  central sub-kpc of the Milky Way
  The four main findings about the age and abundance structure of the Milky Way
bulge based on microlensed dwarf and subgiant stars are: (1) a wide metallicity
distribution with distinct peaks at [Fe/H]=-1.09, -0.63, -0.20, +0.12, +0.41;
(2) a high fraction of intermediate-age to young stars where at [Fe/H]>0 more
than 35 % are younger than 8 Gyr, (3) several episodes of significant star
formation in the bulge 3, 6, 8, and 11 Gyr ago; (4) the `knee' in the
alpha-element abundance trends of the sub-solar metallicity bulge appears to be
located at a slightly higher [Fe/H] (about 0.05 to 0.1 dex) than in the local
thick disk.
