The answers available to this question have stemmed from the Demand-SupplyModel of the Neo-classic economics.
对于第三产业比重为什么会增加，现有的解释主要是新古典经济学供给-需求的分析范式。
2
Demand for the new model is outrunning supply.
新型号的产品供不应求。
《牛津词典》
3
Imports could supply some of the demand while China's rail equipment makers geared up production, but the country's export model works to discourage imports.