Beginning in the 1970s, several suburbs (banlieues) of Paris, (especially those in the north and east) experienced deindustrialisation, as factories closed or moved farther out. The once-thriving residential cités became ghettos for African and Arab immigrants with few skills and high unemployment. At the same time, some neighbourhoods within the city of Paris and the western and southern suburbs successfully shifted their economic base from traditional manufacturing to high-value-added services and high-tech manufacturing, giving these neighbourhoods the highest per-capita incomes in France and among the highest in Europe.[197][198] The resulting widening economic gap between these two areas led to periodic clashes between young residents of the northeast housing projects and the police.[199]