Defining black economy,
If you pay your cleaner or builder in cash or for some reason neglect to tell the taxman which you were paid for a service rendered, you participate in the black or underground economy. Such kind of transaction transactions do not normally demonstrate up in the figures for GDP, so the black economy may mean which a country is much richer where the official data suggest. In the United States & the UK, the black economy includes an estimated 5-10% to GDP, in Italy, it may add 30%. In Russia, the late 1990s estimates of the black economy ranged as high as 50% of GDP.