Coordination of Pps Samples over Time

Probability proportional to size (PPS) sampling finds application in business surveys both for the first stage of a multi-stage design, and for direct sampling of businesses from a list frame. In both cases there is a need to update samples from time to time, while retaining as many units as possible from the old sample. In the second type of application there is also a need for negative coordination of surveys to get an even distribution of response burden. Further requirements on the sampling procedures are simplicity in application and in estimation of variance. We present various permanent random number techniques that meet these requirements and compare them to a few other methods, and present a simulation study on expected overlap.