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 109 increase in storage productivity?

And whereas economic growth theory uses a production value that is net of depreciation, GDP is a gross measure. Thus GDP looks good even when things are falling apart. Being the fastest-growing economy in the 2000s was actually a sign of economic distress, not success, for the United Kingdom.

The economy, as a complex system, cannot logically be indexed by a single figure. In truth, GDP just reflects the perspective of the tax base, because that is how the figures are collected and presumably why the UK Treasury is keen to use it.

Force-feeding an economy's GDP index usually empties its environmental capital first, then its social capital and then whatever cash is left in the bank.