Posting an answer to a question you posed only four hours earlier is a sure sign of unfamiliarity with the literature in that area. Luckily, Ben Muse has pointed me to Andrew K. Rose’s web page, which contains a plethora of links to his papers and various responses on the topic of the GATT/WTO’s effectiveness in liberalizing trade. I’m going to bury my nose in these papers for a day or two.