Sampling on two occasions with probabilities proportional to size without replacement (PPSWOR)

A theory of sampling on two occasions with unequal probabilities and without replacement is presented. Fellegi’s (1963) method, which yields the same selection probabilities for a given unit on each occasion, is used to select the units for the rotation sample. The variances of composite estimators of the population total on the second occasion are developed. Numerical results are presented for small sample sizes and efficiency comparisons are made with a competing strategy.