Longitudinal Research: A World to Explore

This chapter describes some of the issues to be considered when dealing with longitudinal data. Longitudinal data can be defined as data gathered on a set of units over multiple time periods. Longitudinal data can be collected either prospectively or retrospectively, and data can be either qualitative or quantitative. Different ways of deriving repeated observations generate the three main types of longitudinal design: repeated cross-sectional surveys, panel surveys, and retrospective surveys. The world of longitudinal research is thus very heterogeneous. This chapter provides both a summary of advantages and disadvantages of each longitudinal design and some guidelines for authors and researchers.