“…Each good and service may have a production function, meaning some mathematical regularity in how inputs like land, labor, capital, and technology combine to produce televisions, yachts, insurance policies, hamburgers, etc. However, since there is no physical process by which aggregate GNP is produced, nor, from this perspective, is there some way to aggregate and measure physical capital, trying to specify an aggregate production function is seen as nonsensical (Cohen;Harcourt, 2003). Guerrien and Gun (2015, p. 100) note that Paul Samuelson, Nobel laureate in economics, pointed out that aggregate production functions wrongly offer "[…] a statistical test of an accounting identity (which is by definition always true)".…”