A method for determining the dynamics and intensity of average growth

A new statistical method is presented for determining an average growth curve which is valid in the sense of representing both the average dynamic, or tempo, and the average intensity of the growth process studied. In this context, growth curve means either distance, velocity or acceleration curve. The principal idea is to shift individual curves continuously (and non-linearly) in age to an average developmental age scale. Since the resulting curves represent the typical shape rather than individual variations of it, they are of interest for comparisons of different variables of boys and girls and of subgroups. The method is illustrated with longitudinal growth data from the first Zurich longitudinal study.