Douglas Irwin's 1998 paper examines the validity of the opposite tariff hypotheses posed by the Republicans and Democrats in 1890. Irwin looked at historical data to estimate import demand elasticities and export supply elasticities for the US in the years before 1888. He then calculated that tariffs had not reached the maximum revenue rate and that a reduction, not a raise, in the tariff would have reduced revenue and the federal surplus. That confirmed the Democrats' hypothesis and refuted the Republicans'.