A recent study has revealed that illegal work in the building and trades sectors accounts for around a fifth of Berlins gross domestic product, while up to half of those working on the capitals building sites are being paid off-the-books. Construction industry association Fachgemeinschaft Bau, one of the groups behind the study, claims that high taxes have contributed to the steady growth of the black economy in Germany, which this year pulled in 17.5 billion in the capital alone. The situation is particularly acute in the construction industry although other sectors including the hotel and restaurant trade, hairdressing, house cleaning and tutoring are also affected.