Distributed Lag Models: Koyck and Almon Model: An Application on Agricultural Data

Corn is an annual plant that falls into the warm-weather cereal group and ranks second in terms of production among cereals in the world after wheat. Corn is used in many different areas as animal feed and human food. Corn is the most produced cereal plant in Turkey after wheat and barley. The relationship between the production amount and the price of corn plant, which is classified as a field crop, was analyzed using the Koyck and Almon methods. The study data covers the period between 2000-2023, obtained from the Turkish Statistical Institute (TSI). According to the results obtained from the Koyck model, corn production is retrospectively affected by the last three years' prices. The change in corn prices has caused a remarkable effect on production in a period of 6.194 years. Another result obtained from the analysis is that a one TL increase in corn prices in period t increased the production amount by 302283.6 tons. In addition, while a TL increase in price in period t-1 increases the production amount by 2602666.2 tons, a TL increase in price in period t-2 increases the production amount by 224089.2 tons, a TL increase in price in periods t-3, t-4, t-5 and t-6 increases the production amount by 192940.8, 166122, 143031.1 and 123149.7 tons, respectively. Changes in the lagged values of maize prices have a positive effect on production in a decreasing direction. For the suitability of the model, the coefficient of determination (R-2), the adjusted coefficient of determination (R(sic)(2)), the Bayesian Information Criterion (BIC) and the Akaike Information Criterion (AIC) goodness of fit statistics were examined. When the goodness of fit tests is analyzed, R-2=0.940, R(sic)(2)=0.925, and BIC=29.340 for the Koyck model. The Almon model has resulted in R-2 = 0.935, adjusted R-2 = 0.924, and BIC = 29.374. Therefore, it is observed that both models are suitable. However, the research findings indicate that the Koyck model provides slightly better results in explaining the corn production-price relationship.