The largest section of the industrial economy of most persistent concern to governments is that of the network-containing industries (electricity, water, telecommunications, gas, trams and light railways, railways, post and telecommunications). These industries have been at the heart of political debate concerning forms of ownership (nationalization, privatization) and economists and politicians have frequently been at odds over the appropriate pricing and investment rules, and industrial structure for such industries. Often characterized by lumpy, sunk distribution and transmission investments giving rise to natural monopoly characteristics and enjoying large potential economies of scale, investment in these industries has consistently outpaced that in manufacturing industry.