Excerpts from the report: In this study, the feasibility of constructing weather indexes on a comprehensive scale using a modification of Stallings' approach is investigated. For an empirical appraisal of the methodology of measuring yield variation due to weather, a pilot study of limited scope was undertaken. Eventually, it is hoped that weather indexes for yields and production of individual crops and of all crops can be developed. The indexes would be most useful if developed and kept up to date for farm production regions and the United States. Weather indexes for corn yields and production in Iowa from 1929 to 1960 were constructed using a plot data approach. State indexes were developed by aggregating weather indexes for individual Crop Reporting districts. The weather indexes were used in adjusting for the influence of weather the State and district actual yields per harvested acre and total production of corn. Variation in the adjusted yield series is an estimate of the effect of changes in technology.