A flexible logistic growth model with applications in telecommunications

In this paper, the authors develop a four-parameter generalization of the logistic growth curve, the flexible-logistic (FLOG) model. It is shown that the FLOG model is sufficiently general to locate its point of inflection anywhere between its upper and lower bounds; it can offer wide variation in its degree of symmetry for a given point of inflection. Although additional parameters always produce a better within-sample fit, the specific flexibility introduced by the FLOG class of models emphasises the forecast properties by controlling the saturation level and the approach to that level. The model is subjected to a number of theoretical and empirical tests and is applied to three sets of telecommunications data.