Simon Kuznets, a Russian American economist at the University of Pennsylvania, did breakthrough work in the 1930s in measuring national income, "the size of the final net product." He defined net product as follows: "If all the commodities produced and all the direct services rendered during the year are added to their market value, and from the resulting total we subtract the value of that part of the nation's stock of goods that was expended (both as raw materials and as capital equipment) in producing this total, then the remainder constitutes the net product of the national economy of the year." Thus, net product focused on final output only, and excluded business-to-business (B2B) transactions in the supply chain. He expanded his "net output" data to measure Gross National Product (GNP) starting in 1942.