Wahl, Thomas I.

By: Mittelhammer, Ronald C.; Shi, Hongqi; Wahl, Thomas I.
This study revisits the consistent aggregation (over households) property of almost ideal demand system (AIDS) models and presents a method to explicitly account for expenditure aggregation bias when estimating the aggregate AIDS model with time-series data. Ignoring aggregation bias can lead to biased and inconsistent parameter estimates and can cause aggregate demand functions to be inconsistent with the demand functions at the individual household level. Recognizing the general limited information contained in aggregate time-series data for explicitly modeling aggregation bias, we present a new method of constructing an aggregation bias term that is derived from the proportions of household in different income groups. This information is generally available in developed economies. We use this framework to estimate aggregate meat demand within a complete demand system based on U.S. annual expenditure data.
By: Devadoss, Stephen; Kropf, Jurgen; Wahl, Thomas I.
A world sugar model consisting of 21 countries was developed to determine the effects of NAFTA of U.S. and Mexican sugar markets and to quantify the trade creation and diversion effects on U.S. imports from Mexico. Mexican sugar production increases under NAFTA, causing Mexico to become a net exporter. NAFTA induces sugar imports from Mexico to displace U.S. production, to meet demand expansion, and also to divert U.S. imports from other foreign suppliers to Mexico. Effects of NAFTA on the U.S. sugar market are small because of the side agreements which limit Mexican exports and which include corn sweetener consumption when computing Mexico's production surplus.
By: Wahl, Thomas I.; Hayes, Dermot J.; Johnson, Stanley R.
The Japanese pork market is protected by a complex set of restrictions, including a variable levy and an import tariff. The combination of these policies distorts the quantity, price, and form of Japanese pork imports. An important issue relevant to the liberalization of the Japanese pork market is the accurate measurement of the price wedge between Japanese and world pork prices. The analysis indicates that the tariff equivalent of the price wedge over the 1986-88 period was 44%. If the tariff equivalent of the price wedge is reduced over a ten-year period, Japanese pork imports are projected to increase by over 39% initially and by over 215% compared to baseline projections by the year 2000. Producer welfare can be maintained by a deficiency payment scheme. A less costly alternative is an industry buffer scheme, which maintains the level of the pork industry for two years and then implements a declining deficiency payment scheme that limits the decrease in production levels to 5% per year.