Weber-Fechner law

Perceived difference is not the same as actual difference. We think 10 to 20 is a bigger change than 1000 to 1010.

Consequences

Weber-Fechner law can explain the increasing levels of public expenditures in mature democracies. Election after election, voters demand more public goods to be effectively impressed; therefore, politicians try to increase the magnitude of this "signal" of competence - the size and composition of public expenditures - in order to collect more votes.