Furthermore, Henderson (2014) 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, 2012). Policies to invest in transport links between cities and improve urban-rural links have been shown to improve balanced productivity (AfDB, OECD and UNDP, 2016; UNECA, 2013). 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, 2001).