Drawing upon historical data, Robert Fogel found that the impact of railroads on the iron and steel industries was minimal: from 1840 to 1860, railroad production used less than five percent of the total pig iron produced.
根据历史数据绘制图表，罗伯特·福格尔发现，铁路对于钢铁工业的影响是最小的：在1840年到1860年间，铁路产品使用了不到5%的当时所生产的生铁（pig iron）。