Productivity Growth in Grain Production in the United States, 1840–60 and 1900–10

William N. Parker, Output, Employment, and Productivity in the United States after 1800 (NBER, 1966), chap. 13, https://www.nber.org/books-and-chapters/output-employment-and-productivity-united-states-after-1800/productivity-growth-grain-production-united-states-1840-60-and-1900-10.