This paper is divided into two parts. In the first part we discuss our direct findings from a descriptive study of the wave-seam effect. The first section demonstrates directly that while absolute rates of change are strongly influenced by the wave-seam effect, that the correlations of the rates of change are not. In the second part of we discuss some of the most plausible sources of the wave-seam effect in the SIPP and their implications for analysis. In particular, we discuss the constant wave response, a form of response bias (measurement error) that may be present in many retrospective surveys, but which will be revealed only in surveys like the SIPP that are both retrospective and longitudinal.