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Modifying composite weighting when PPS samples have already been chosen.

Keywords: sample design, sampling weights, PPS, National Agricultural Statistics Service, Agricultural Yield

The late spring of 2008 experienced a high level of flooding in the Midwest. Areas with tributaries to the upper Mississippi River suffered the most damage. As a result, the National Agricultural Statistics Service (NASS) decided to re-interview members of the June land-based survey, as well as add samples to two surveys that are used for forecasting crop yields. One survey is based on an area frame, the other is a probability list-based survey. The original samples were selected using modified Probability Proportional to Size designs for both surveys. The indication provided from the probability list based survey uses a composite weight between two separate portions of the survey. Adding records to an existing sample caused a composite weight on an existing composite weight to be used. It will be demonstrated how the multiple-composite weighting was constructed as well as weighting issues that arose and how those issues were resolved.