A look at the constancy principle under changing market conditions

How the principle of relative constancy of media spending has fared across time is explored in this study. The authors use both income‐share and time‐trend regression models to study consumer spending on media in the U.S. since 1929. They conclude that the principle of relative constancy clearly held from 1929 to 1974, but that evidence since that time (which corresponds with the emergence of cable television and VCRs) is unclear, although partially supporting the principle.