In combination with sluggish economic development, the financial crisis and the debt crisis that it triggered have contributed to the fact that tax evasion, tax fraud and tax avoidance are recognised as a serious problem. The revelations by “Offshore Leaks” through the International Consortium of Investigative Journalists (ICIJ) and investigative journalism on the one hand and the work of NGOs, for example by the Tax Justice Network, on the other have provided essential contributions that have increasingly brought the discussion out into the public. As a result the dimensions of the massive offshore fortunes have become known and the resulting tax shortfalls in the nation states have been expressed. The rapid escalation of offshore wealth also seems threatening. After the financial crisis, an increase of 28% was recorded in a period of just five years, between 2008 and 2013.<br />The increasingly unequal international distribution of wealth is now leading economists to comprehensive research work and preliminary estimates. There is hardly any data on the costs caused by tax havens, in particular through the massive tax shortfalls. The necessary data is taken as a basis from various available scientific sources. Filling the gaps in the data and making the information available should not just be task of scientists, but rather also of politics.