原文：Throughout the past two decades, GATT (the General Agreement on Tariffs and Trade ) has been increasingly preoccupied with the trading problems and needs of the developing countries, which accounts for more than two-thirds of its membership.
译

原文：Throughout the past two decades, GATT (the General Agreement on Tariffs and Trade ) has been increasingly preoccupied with the trading problems and needs of the developing countries, which accounts for more than two-thirds of its membership.
译文:在过去的二十年中，关贸总协定越来越忙于解决发展中国家的贸易问题和需要，他们占成员国总数2/3以上。

修改：在过去的二十年中， 关贸总协定越来越关注占成员国总数 2／3 以上发展中国家的贸易问题和需要。（“关注” 1 分， 句序调整 1 分）