The area of the US stretching from Pittsburgh to St Louis, containing a large concentration of traditional, but declining, heavy industries. The rustbelt suffers from high obsolescence and relatively strong unionization of the labour force, both of which have encouraged a tendency for economic activity to shift to the South and the West. Parts of the rust belt have suffered severe population loss and urban decay. Detroit, for example, suffered a decline of 62 per cent in its population between its peak in 1950 and 2012.