The National Park Service says that in eighteen twenty-two, trade along the Santa Fe Trail totaled fifteen thousand dollars.

VOA: special.2009.03.30

On the trade side, service sector is the one which has been booming the most.

从贸易角度来说，是第三产业,发展最迅速。

普林斯顿公开课 - 国际座谈会课程节选