英语翻译In a perfect world,trade patterns should be determined b

英语翻译
In a perfect world,trade patterns should be determined by comparative advantage:the comparative cost of making different goods yourself as opposed to buying them from various countries.
对冒号后边的部分有些困惑（as在这里是什么词性）

as opposed to与…截然相反；对照
这是一个固定搭配,不好说是什么词性.
可以理解成as is opposed to吧,连词,相当于which