  The paucity of observed dwarf galaxies in the Local Group relative to the
abundance of predicted dark matter halos remains one of the greatest puzzles of
the LCDM paradigm. Solving this puzzle now requires not only matching the
numbers of objects but also understanding the details of their star formation
histories. We present a summary of such histories derived from the HST data
using the color-magnitude diagram fitting method. To reduce observational
uncertainties, we condense the data into five cumulative parameters -- the
fractions of stellar mass formed in the last 1, 2, 5, and 10 Gyr, and the mean
stellar age. We interpret the new data with a phenomenological model based on
the mass assembly histories of dark matter halos and the Schmidt law of star
formation. The model correctly predicts the radial distribution of the dwarfs
and the fractions of stars formed in the last 5 and 10 Gyr. However, in order
to be consistent with the observations, the model requires a significant amount
of recent star formation in the last 2 Gyr. Within the framework of our model,
this prolonged star formation can be achieved by adding a stochastic variation
in the density threshold of the star formation law. The model results are not
sensitive to late gas accretion, the slope of the Schmidt law, or the details
of cosmic reionization. A few discrepancies still remain: our model typically
predicts too large stellar masses, only a modest population of ultra-faint
dwarfs, and a small number of dwarfs with anomalously young stellar
populations. Nevertheless, the observed star formation histories of Local Group
dwarfs are generally consistent the expected star formation in cold dark matter
halos.
