Gross domestic product (GDP) is as poor a measure of the economy as it is of welfare (Nature 468, 370–371; 2010).

Quantifying the concept of 'the economy' is contentious because of arbitrary decisions as to what to include, and because of a drift when indexing to constant prices. For example, should the jump in price from Walkman to iPod be classed as inflation or as a 10 increase in storage productivity?