Converting Old Money to Today: Why There's No Single Answer
If a painting sold for 400 francs in 1890, how much is that in today's money? It seems like there should be a single number—but economic historians use at least four different measures: real price (CPI), labor value (wages), income value (GDP per capita), and economic share (share of GDP). Pick a different measure, and the answer shifts by 54-fold or more—162-fold for a national-scale deal like the Alaska Purchase.