For the supplementary quantity the quantity units recommended by the World Customs Organization (WCO) (see Annex I) for individual commodities (6-digit sub-headings) are enforced in order to allow comparability across countries. The quantity information reported for a particular commodity has to be reported in the WCO recommended unit (WCO RU) or it must be possible to convert the reported quantity unit into the WCO RU. Otherwise the quantity information is disregarded. Previously, there was no procedure in place to ensure that the quantity information for individual commodities would follow a specific quantity unit.

非常感谢！我用联合国贸易数据库在求进出口数据时，里面主要有以下几项：Year、Reporter Code、Trade Flow Code        、Partner Code、Classification、Commodity Code、Quantity Unit Code        、Supplementary Quantity、Netweight (kg)、Value、Estimation Code
我求进出口之和时，直接把每年value那列相加，为什么求出来的结果是别人的两倍，一直没有找到原因，不知您能给点建议不？谢谢！

你把对方国家有个world删除掉就好，否则肯定2倍。

注意对方国家 eu和world

非常感谢！真佩服您！您真是帮我解决大问题了！琢磨了几天都没想通，问我们老师他也没给出解决办法，再次表示感谢！以后有问题可能还需要向您请教！