Contemporary American economic historians have challenged this conventional view. The respective findings of Robert Fogel and Albert Fishlow do not support Rostow’s claim that railroads stimulated widespread industrialization by increasing demand for coal, iron, and machinery. 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. In addition, Fogel argues, only six percent of total coal production from 1840 to 1860 was consumed by railroads through consumption of iron products.[12] Like Fogel, Fishlow showed that most railroads used very little coal during this time period because they were able to burn wood instead.[13] Fishlow also found that iron used by railroads was only 20% of net consumption in the 1850s.