The onset of industrial copper mining on the Copperbelt in the late 1920s triggered rapid urbanisation. Although urbanisation was overestimated during the colonial period, it was substantial. Mining townships on the Copperbelt soon dwarfed existing centres of population and continued to grow rapidly following Zambian independence. Economic decline in the Copperbelt from the 1970s to the 1990s has altered patterns of urban development, but the country's population remains concentrated around the railway and roads running south from the Copperbelt through Kapiri Mposhi, Lusaka, Choma and Livingstone.