قياس أثر تغيرات بعض محددات عرض محصول القطن في العراق باستخدام نموذج التكامل المشترك و تصحيح الخطأ للمدة 1970 -2010

الملخص EN

Coton is considered as one of the most important industrial crop which puts it in the second rank after nutritional crops in the world.

The importance of cotton comes from the ability to use its fibers in the best type of fabrics, due their durability, smoothness, and flexibility, aside from its use in medicine, furniture, and vegetable oil industry.

This study aimed to estimate cotton supply response in Iraq for someof its determinants the period 1970-2010 using the concept of cointegration and error correction.

To accomplish this aim, main factors that affecting cotton acreage supply response were determined which included: cotton price, price of competitive crop (maize), and irrigation water.

Time series of the model were analyzed using augmented Dickey Fuller (ADF) test to avoid the superiors regression problem.

Results of this test revealed the non-stationary nature of the model time series in their level and stationary in their first difference, and they were all cointegrated, with the presence of long-run equilibrium relationship between cotton-cultivated area (CCA) and its determinants.

To estimate the effects of the short- and long-run determinants on CCA, vector error correction model (VECM) was used.

The results unveiled the significance of cotton price, maize price, and irrigation water; all of which represented 82% of the changes in CCA in Iraq.

The results also demonstrated the presence of short-run relationship between CCA and its determinants.

In the light of VECM results, CCA can be corrected from disequilibrium in every previous period by -0.1999 towards its equilibrium value.

The speed of adjustment to equilibrium takes 5 years after the shock in the model which results from the change in one of the explanatory variables.

Estimated elasticities indicated that price elasticity of cotton in relation to its price were 0.44515 and 0.65421 in the short- and long-run respectively, while cross elasticities of cotton were -0.20987 and -0.4875 in the short- and long-run respectively.

Cotton supply elasticities in relation to irrigation water were 0.38223 in the short-run and 0.58469 in the long-run.

As the elasticity values were less than one, the supply of this crop can be described as enelastic.