After World War II, Ghent and Antwerp experienced a rapid expansion of the chemical and petroleum industries. The 1973 and 1979 oil crises sent the economy into a recession; it was particularly prolonged in Wallonia, where the steel industry had become less competitive and experienced a serious decline. In the 1980s and 1990s, the economic center of the country continued to shift northwards and is now concentrated in the populous Flemish Diamond area.