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This article begins by presenting the properties of the income polarisation indicators developed by Foster-Wolfson and Esteban-Ray, and their scope and limits. The two polarisation and inequality criteria appear complementary but different insofar as the Pigou-Dalton transfer principle is alien to the polarisation concept. We next apply these indicators to French data in order to test their explanatory capacity by comparing their informative value with the results of closer analysis of population characteristics. We use this opportunity to look at the relevance of the increase in wage income polarisation in the nineties. Job polarisation appears to have made a significant contribution to this phenomenon.