In the context of a growing international economic integration, taxation becomes a more and more central factor in the competition of regions and countries for international investment and skilled employees. From that perspective, in addition to the effective level of company taxation also the effective tax burden on highly skilled employees is important: Due to the growing international mobility of highly skilled employees, these employees compare net incomes and force companies to bear international and interregional differences in compensation tax burdens. The present research project will analyse effective tax burdens on corporations and on highly skilled employees in 64 different locations from 17 European countries and the U.S. for 2004 and 2005. Thereby, it will update and geographically extend the IBC Taxation Index, which has been published first in 2003 for the years starting in 2001. Furthermore, the research project will deliver quantitative input data for additional studies that explore the impact of taxation as an international and interregional growth determinant.