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Tests of lepton-universality as rate ratios in transitions can be predicted very accurately in the Standard Model. The deficits with respect to expectations reported by the LHCb experiment in muon-to-electron ratios of the decay rates thus point to genuine manifestations of lepton nonuniversal new physics. In this paper, we analyze these measurements in the context of effective field theory. First, we discuss the interplay of the different operators in and and provide predictions for in the Standard Model and in new-physics scenarios that can explain . We also provide approximate numerical formulas for these observables in bins of interest as functions of the relevant Wilson coefficients. Secondly, we perform frequentist fits to and . The Standard Model disagrees with these measurements at significance. We find excellent fits in scenarios with combinations of operators, with …