"A study by a free-market thinktank, the Institute for Economic Affairs, estimated that paid work not declared to the taxman was worth 10% of national income in 2012, half the level in Italy, Greece and Spain. The report, by economists Friedrich Schneider and Colin Williams, found that the UK's shadow economy was smaller than the 13.4% average for the 34 developed nations in the Organisation for Economic Cooperation and Development. The UK rate peaked at 13% in 1997-98." Larry Elliott, 'The Guardian'