Non-linear panel estimation of import quotas: The evolution of quota premiums under the ATC

We develop a panel-based inequality constrained least-squares (ICLS) framework for estimating the export tax equivalent (ETE) of quotas where the ETEs vary over time. Working with a panel of bilateral data on textile and clothing trade,underlying bilateral tariffs, and the country-pair coverage of quotas under the WTO's Agreement on Textiles and Clothing (ATC), we use this framework to examine the evolution of market access conditions in the textile and clothing sectors. Our estimating framework takes advantage of the panel nature of trade data when calculating export tax equivalents while allowing for inequality constraints on the quota premium estimates. We also implement quadrature methods for calculating confidence intervals for our regression-based NTB measures.