Double Counting
Counting events or occurrences more than once — seen in accounting as a mathematical error, but in macroeconomics as an embedded challenge where boundary problems and logical unit problems arise (i.e. household input is institutional output).
Origin
The problem became a central challenge in developing national income accounting. Simon Kuznets, the economist who pioneered the gross national product framework for the U.S. in the 1930s and 1940s, identified double counting as a key trap: simply adding all firms' gross sales would count intermediate goods — steel, flour, fuel — multiple times. To solve it, Kuznets formalized the value-added method: each firm's purchased inputs are subtracted from its gross output, yielding only net new production at each stage.