NOTE: Although the following article has not been revised for this edition of the Encyclopedia, the substantive coverage is currently appropriate. The editors have provided a list of recent works at the end of the article to facilitate research and exploration of the topic. According to Heckman and Singer, "Longitudinal data are widely and uncritically regarded as a panacea . . . The conventional wisdom in social science equates 'longitudinal' with 'good' and discussion of the issue rarely rises above that level" (1985, p. ix).

There is probably no methodological maxim in sociology more often repeated than the call for longitudinal data. From the work of David Hume more than 250 years ago, to the exhortations for a "radical reformation" in the work of Stanley Lieberson (1985, p. xiii), the importance of longitudinal data has been emphasized and reemphasized. Yet it is doubtful that there is an area of sociological method in...