Logistic versus decaying exponential equations for describing mail survey response curves: A conceptual rationale and reanalysis

Both the logistic and decaying exponential equations have been used to describe the accumulated growth curve of mail survey returns. While empirical fits have been presented for both curves, a conceptual rationale for either curve is lacking in the mail survey research literature. This paper thus presents a conceptual reason, in addition to empirical fits, for using the decaying exponential equation rather than the logistic equation in describing the accumulated mail survey response curve. It also shows that past comparisons of the logistic and decaying exponential equations have been inappropriate because of the use of different asymptotes. Based on an examination of two decaying exponential equation forms, a strategy for future research is suggested.