Vietnam scored a victory Monday in its first challenge at the World Trade Organization against the United States over anti-dumping measures imposed by Washington on frozen shrimps. The trade watchdog found that Washington\'s use of the so-called zeroing method to calculate dumping margins were \"inconsistent\" with international trade rules, and must therefore halt such action. The United States has lost several major cases at the WTO related to the zeroing method -- which involves counting negative values as zero when calculating an average -- including against Brazil and the European Union. According to complainants, the zeroing method allows Washington to increase its estimate of the degree of dumping on its markets. Dumping involves the sale of items abroad at less than the cost price in their domestic market.