Rich economies are also less dependent on oil than they were, and so less sensitive to swing in the oil price.
在这句话中，than 后边接的是they were, than的词性是什么？than具备介词、连词两个词性。
Rich economies are also less dependent on oil than they were , and so less sensitive to swing in the oil price.
这回明显了，你说它是连词还是介词呢？显然是连词呗！
