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This paper outlines briefly the historical development of ideas related to longitudinal studies and their advantages over cross-sectional studies. Then it points out a few complicating factors that arise with the analysis of longitudinal data and highlights some of the approaches adopted to manage those complicating factors and illustrated in the papers included in this Special Issue. The overall aim is to promote a better understanding of the information that longitudinal data provide and of the suitable techniques needed to analyze such data.
Fernando Rajulton (Mon,) studied this question.