Martin E. Abel

Harmonic Analysis of Seasonal Variation with an Application to Hog Production

Abstract Several methods for analyzing seasonal variation are available. Most common among these are methods based on moving averages. One serious shortcoming of moving average methods is that the process of moving averages can introduce a fictitious degree of regularity into the seasonal pattern. An alternative method, harmonic analysis, is presented in this paper with an application to hog production data. The investigation illustrates the flexibility of harmonic analysis for measurement of patterns of seasonal variation. Hypotheses concerning changes in amplitude and phasing of the seasonal pattern are tested and a discussion of these procedures is presented.

Price Discrimination in the World Trade of Agricultural Commodities

Price discrimination between domestic and export markets by exporters of agricultural commodities is a long-established practice. It has been common for exporters to charge lower prices in world markets than in home markets. In recent years, some countries that are major importers of agricultural products have adopted minimum-import-price schemes to insulate their domestic prices from world prices. The effects of such trade barriers on the price-discrimination practices of exporters is examined. As minimum-import-price schemes become more widespread, it may be more profitable for exporters to charge higher prices in export markets than in their own domestic markets. The implications of reversing the direction of price discrimination are explored for exporters, importers employing minimum-import-price schemes, and importers with no or minimal trade barriers.

Measuring Changes in International Trade

This article presents and discusses a zero-axial skew-symmetric matrix (ZSM) that is useful for measuring changes in international trade. Such a matrix, E, has the property that the element eij, which represents exports from country i to country j, is equal to —eji, except that eii = 0. It provides a convenient and analytically useful way to present data on international trade among countries; both imports and exports appear in one matrix and separate matrices are not required. The ZSM can be used to measure changes in the level and composition of trade over a period of time. Transition matrices can be computed from long time-series of international trade data. The coefficients of these transition matrices provide useful data for summarizing changes in trade patterns. Both trends and annual variations in exports (or imports) from (or by) countries or regions can be measured.