Modelo econométrico colombia

Agricultural & Applied Economics Association

Cobweb Models Author(s): Frederick V. Waugh Source: Journal of Farm Economics, Vol. 46, No. 4 (Nov., 1964), pp. 732-750 Published by: Oxford University Press on behalf of the Agricultural & Applied Economics Association Stable URL: http://www.jstor.org/stable/1236509 . Accessed: 30/05/2011 20:46
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CobwebModels
V. FRmDEmcK WAUGH*
In recent years, economists have become much interested in recursive models. This interest stems from a growing need for long-term economic projections and for forecasting the probable effects of economic programs and policies. In a dynamic world, past and present conditions help shape futureconditions. Perhaps the simplest recursive model is the two-dimensional "cobweb diagram," discussed by Ezekiel in 1938. The present paper attempts to generalize the simple cobweb model somewhat. It considers some effects of price supports. It discusses multidimensional cobwebs to describe simultaneous adjustments in prices and outputs of a number of commodities. And it allows for time trends in thevariables.

1938, still stands as a landmark in the theory of prices and production. His theory was realistic and operational. It was based upon the flood of statistical findings in the 1920's, following the pioneering work of Moore. Economists are again becoming interested in simple cobweb models and in more elaborate, but related, recursive models. It seems appropriate to review cobweb models inview of developments of the past 25 years in economics, statistics, and data processing, and in view of current needs for program analysis and economic projections. History The classic paper on the cobweb theorem was published by Ezekiel' in 1938. In that paper, Ezekiel pointed out that the basic idea of a cobweb model was implied in much of the excellent econometric research of the 1920's, and thatit had been discussed by several writers. As early as 1917, Moore2 had demonstrated that the current price of cotton was determined by the size of the current crop; while the current crop was influenced by the previous year's price. Other studies of Moore showed that this same pattern applied to potatoes and to other farm products. Economists in the former Bureau of Agricultural Economics(including Ezekiel) and in the colleges found similar patterns for a wide variety of farm products. And, in 1928, Hanau3 found that cur*I in this field: Mordecai gratefully acknowledge suggestions from four pioneers Ezekiel, Wassily Leontief, Jan Tinbergen, and Herman Wold; as well as from my W. Neill present colleagues in the Economic Research Service, Shlomo Reutlinger, Schaller, and Forrest Walters,...