  Predictions of antineutrino fluxes produced by fission isotopes in a nuclear
reactor have recently received increased scrutiny due to observed differences
in predicted and measured inverse beta decay (IBD) yields, referred to as the
'reactor antineutrino flux anomaly.' In this paper, global fits are applied to
existing IBD yield measurements to produce constraints on antineutrino
production by individual plutonium and uranium fission isotopes. We find that
fits including measurements from highly 235U-enriched cores and fits including
Daya Bay's new fuel evolution result produce discrepant best-fit IBD yields for
235U and 239Pu. This discrepancy can be alleviated in a global analysis of all
datasets through simultaneous fitting of 239Pu, 235U, and 238U yields. The
measured IBD yield of U238 in this analysis is (7.02 +/- 1.65) x 10^-43
cm2/fission, nearly two standard deviations below existing predictions. Future
hypothetical IBD yield measurements by short-baseline reactor experiments are
examined to determine their possible impact on global understanding of isotopic
IBD yields. It is found that future improved short-baseline IBD yield
measurements at both high-enriched and low-enriched cores can significantly
improve constraints for 235U, 238U, and 239Pu, providing comparable or superior
precision to existing conversion- and summation-based antineutrino flux
predictions. Systematic and experimental requirements for these future
measurements are also investigated.
