Inflation is always a little lower than it seems once you allow for such substitutions. But one group of people can’t play that game.
In a laboratory in College Station, Texas, in 1990, six lab rats pressed levers and lapped at tubes as root beer and tonic water were released. They were participating in the quest for an elusive quarry: the Giffen good. Robert Giffen was born in Lanarkshire in 1837, the year of Queen Victoria’s accession. He would become by turns assistant editor at The Economist, chief statistician at the Board of Trade, President of the Royal Statistical Society and co‑founder of the...