Reactor antineutrinos have been indispensable for our
understanding of neutrino mass and mixing. At the same time,
discrepancies between the observed and predicted reactor
$\overline{\nu}_{e}$ rate and energy spectra have grown as the
precision of these measurements has improved. Measurements of
the electrons emitted following fission result in the most
precise predictions for the corresponding $\overline{\nu}_{e}$
flux, and our understanding of the potential systematic
differences between the fission $e^-$ and $\overline{\nu}_{e}$
fluxes has improved. Measurements of individual fission daughter
isotopes and their decays are fraught with uncertainties, yet
still provide insight into these discrepancies. Detailed
comparisons of $\overline{\nu}_{e}$ measurements among reactors
are also shedding new light on this topic.