Current models proposed in planetary aeronomy involve a large variety of possible gaseous mixtures which are subjected to charged particle bombardment. To facilitate the analysis of such problems, we propose a phenomenological approach to electron degradation in gaseous mixtures that is a natural outgrowth of recent studies of yield spectra in pure gases. Existing parameterized yield spectra for a variety of gases, computed by a discrete energy bin method, are used as the basis for constructing a parameterized composite yield spectrum for an arbitrary mixture. For mixtures involving O2, N2, Ar, and He, results are obtained that reproduce the values computed from a complete discrete degradation computation at a few sample mixtures for initial energies greater than 100 eV. Effects of collisional deactivation are not included. An important value of the method lies in its low cost, making it appropriate for widespread application to aeronomy in the energy regions above a few times thresholds. The structure inherent at low energies makes scaling difficult there, but existing discrete deposition codes are easily applied for mixtures at energies below 100eV.