Corruption is a very large ‘industry’. Yet until very recently, it was virtually impossible to venture an estimate of the extent of corrupt annual transactions. In fact, only a few years ago, corruption was regarded as impossible to measure. Thanks to the ‘explosion’ in measurement approaches and actual data in this field, at least it is now possible to estimate rough orders of magnitude. Our focus is on measuring the extent of bribery from the private sector (firms and individuals) to the public sector.
A conservative approach to such measurement gives an estimate for annual worldwide bribery of about US $1 trillion dollars (US $1,000 billion.). We obtain figures on bribes from worldwide surveys of enterprises, which ask questions about bribes paid for the operations of the firm (licenses, regulations, etc.), as well as bribes paid to get favorable decisions on public procurement. Further, an estimate on bribes paid by household users of public services is derived from governance and anti-corruption diagnostic surveys.
There is a margin of error in all these estimates, so we should regard them as preliminary orders of magnitude. But the main point is that this is not a relatively small phenomena of a few billion dollars – far from it.
Source: The Word Bank