Appendix B: Indexes and Values for Intermediate Classes, 1879–1923

Robert E. Lipsey, Price and Quantity Trends in the Foreign Trade of the United States (Princeton University Press, 1963), https://www.nber.org/books-and-chapters/price-and-quantity-trends-foreign-trade-united-states/appendix-b-indexes-and-values-intermediate-classes-1879-1923.