In panel surveys, it is often important to evaluate response rates at several levels, including the aggregate (unit) level, panel-specific and wave-specificm-specific levels. This paper considers these issues in two ways. First, we provide a detailed review of the relevant literature, with special attention devoted to the abovementioned distinctions, and to survey characteristics and predictor variables associated with variability in response rates. Second, we present analyses of patterns of reporting rates in the U.S. Consumer Expenditure (CE) Interview Survey. In the CE Interview Survey, consumer units (roughly equivalent to households) are asked to provide month-by-month reports of the amounts of money spent on each of a large number of items. Reported expenditures are recorded at a relatively fine level of detail defined by the six-digit Universal Classification Code (UCC). The analyses place special emphasis on the relationships of reporting rates with interviewer characteristics, the wave, the recall month and the distance between the recall month and the interview month.