This article by Louis Chauvel and Anne Hartung features in the World Social Science Report 2016. The living conditions and well-being of the middle class are traditionally considered an expression of how society is progressing. Yet growing inequality and the polarization of incomes observed in Western countries as a result of globalization, the recession and rapid technological change are leading to what has been described as a ‘malaise of the middle class’. This contribution presents the evolution of the income distribution in selected Western countries, and discusses the possible impact of the threat created by downward mobility and the erosion of the middle class in today’s society.