Crop producers face many decisions each year about the quantity and quality of inputs to use, the purchasing of these inputs, and the timing of production operations. Because their time for gathering and analyzing information on which to base management decisions is limited, they need to know which decision, areas have the greatest impact on profitability. A set of detailed and accurate records of production, costs, and returns from a group of producers growing corn and soybeans in Iowa over a three-year period was.available from Iowa State University Extension. This information was used to assess the relative importance of various management areas on the profits earned. By comparing time.series as well.as cross sectional data, the Influence of random annual events such as weather is diminished. The objectives of the analysis that Is summarized in this paper were: (a) to test the stability of the relative economic,results of a set of crop producers over time. (b) to quantify the relative impact of various crop management areas on profitability. (c) to test the relationships among the various management areas themselves.