Objectives: This article discusses some of the benefits and challenges of data from a longitudinal panel as exemplified by the National Population Health Survey (NPHS).
Data source: The NPHS collects both cross-sectional and longitudinal data from a sample of randomly selected individuals. The longitudinal sample will be reinterviewed every 2 years for up to 20 years. Two NPHS cycles have been completed: cycle 1 in 1994/95 and cycle 2 in 1996/97.
Summary: Selected findings from the NPHS are presented to illustrate the benefits of longitudinal data. An overview of questionnaire content, collection methods follows, and sample design is provided. A summary of response rates is followed by a discussion of the methods used to maintain response and to adjust the survey weights in order to reduce nonresponse bias. Confidentiality, dissemination, inconsistencies in reporting, proxy reporting and changes in coding conventions are also discussed.