furthermore henderson argues that we do not yet know enough about the economic dynamics of urban systems to attempt to influence them and such attempts risk a major policy error very large investments may therefore be needed for some smaller cities to reach this threshold altbeker mckeown and bernstein policies to invest in transport links between cities and improve urbanrural links have been shown to improve balanced productivity afdb oecd and undp uneca additionally industries with intensive use of immobile primary factors that are not heavily dependent on other firms for intermediate goods and services may prefer to locate in smaller cities if infrastructure is improved henderson shalzi and venables