Modeling weekly Canary tomato exports

The European tomato market is characterized by a constant process of dynamic adjustment towards equilibrium. Furthermore, Canary Island tomato exports cause a high seasonal impact on market prices in the winter period. In these circumstances, an adequate distribution of weekly shipments throughout the year could contribute to maximize producers' profits. Moreover, Canary export levels show some degree of instability, clearly related to the changes in the EU trade rules and there is a long period, in the summer, without exports. The aim of this article is to analyze the long-term movements and, particularly, the seasonal pattern of Canary Island tomato exports throughout the last two decades. To observe more clearly the exporter's decisions, weekly data have been used. The instabilities in the long-term behavior of the series and the specific nature of the seasonal pattern should be taken into account, to capture the performance of exports accurately. Thus, this analysis is carried out using the structural approach to time series analysis, and the usefulness of spline functions as a tool capable of modeling seasonal variations for which the period does not remain the same over time is shown.