This study examines three alternative models of correcting for heteroskedasticity in wheat yield: the time trend variance, the GARCH, and an econometric model that includes the potential sources of heteroskedasticity. Nonnested test results suggest that modeling the sources of heteroskedasticity...

Even if the original version of the Armington model is simple and plausible in estimation, the single CES and homotheticity assumptions are too restrictive for practical application and give biased price elasticities. This paper develops a generalized Armington model, which relaxes the single...