Longitudinal data suffer from the same statistical problems as cross-sectional data. True estimates of means and sums require adjustments for sampling rates or, in the case of census data, nonresponse rates. Whereas in cross-sectional data the standard method of adjustment is the attachment of weights to individual observations, this method does not work in the case of transition matrices calculated from longitudinal data. The reason for this is the unavoidable misclassification of farms as exiters, entrants, and continuers that arises from nonresponse. The method presented here offers a simple algorithm based on four assumptions for making the necessary correction. The algorithm is easily implemented with standard spreadsheet software.