Current models of antineutrino production in nuclear reactors predict absolute detection rates and energy spectra at odds with the existing body of direct reactor antineutrino measurements.  In this talk, I will overview the recent reactor antineutrino measurements and theoretical work that have laid bare these discrepancies, while also discussing primary popular explanations for the disagreements.  I will focus on recent measurements by the Daya Bay experiment that have particular relevance in distinguishing between these differing hypotheses.  The Daya Bay experiment has utilized eight functionally identical underground detectors to sample reactor antineutrino fluxes from three pairs of nuclear reactors in South China, accruing, in the past four years of operation, the largest reactor antineutrino sample to date.  In its most recent result, Daya Bay has measured correlations between reactor core fuel evolution and changes in its detected antineutrino flux and spectrum, enabling new constraints on antineutrino production by the primary fission isotopes U-235 and Pu-239.  I will close by discussing how future reactor antineutrino experiments, like PROSPECT, can use highly-enriched uranium reactors to further elucidate antineutrino production by the dominant fission isotopes.