Income inequalities have been growing significantly within countries over the past two decades or so. This new report presents a timely assessment of this issue, based on new data and economic analysis and with full technical annexes. It looks at the extent of this phenomenon and its sustainability, analysing factors at work and examining the extent to which it may worsen as a result of the ongoing food and financial crises. The report sheds light on the causes of 'excessive' inequality, and in particular the possible role of financial market deregulation. It also examines the extent to which traditional policies and institutions can still address excessive market-driven inequalities, and whether traditional redistribution systems are being eroded as a result of a general trend towards lower taxation on high incomes. In conclusion, the report considers policy reforms that could reduce the risk of rising "excessive" inequalities while at the same time maintaining economic dynamism.