Advances in longitudinal data analysis: An historical perspective
There have been remarkable developments in statistical methodology for longitudinal data analysis in the past 25 to 30 years. Statisticians and empirical researchers now have access to an increasingly sophisticated toolbox of methods. As might be expected, there has been a lag between the recent developments that have appeared in the statistical journals and their widespread application to substantive problems. At least part of the reason why these advances have been somewhat slow to move into the mainstream is their limited implementation in widely available standard computer software. Recently, however, the introduction of new programs for analyzing multivariate and longitudinal data has made many of these methods far more accessible to statisticians and empirical researchers alike. Also, because statistical software is constantly evolving, we can anticipate that many of the more recent advances will soon be implemented. Thus, the outlook is bright that modern methods for longitudinal analysis will be applied more widely and across a broader spectrum of disciplines.