It is shown that scaling behavior at short distances of the $c$ -number part of the
commutator of the hadronic electromagnetic current does not in general entail
asymptotic constancy of the branching ratio $$ R(s)\equiv\sigma(e^-e^+\tohadrons)/ \sigma(e^-e^+\to\mu^-\mu^+), $$$s=(p_{e^-}+p_{e^+})^2$at large$s$. It is found that the structure of the leading singularity of the current commutator near the light cone is directly related to the asymptotic behavior of the function$$ \displaystyle\langle R\rangle(s)\equiv s^{-1}\int_{4m_\pi^2}^sR(s')\,ds' $$as$s\to\infty$.