Glaeser (1996) mentions that urban workers of all education level command higher wages relative to their rural counterparts (i.e., an urban wage premium). Similarly, Moretti (2012,Ch. 34 ) shows that workers of all education levels earn more in cities with more highly educated workers. Figure 1 corroborates this. Standard economic theory associates higher wages with higher productivity. Figure 1: Wage Rates and Metropolitan Population* Provide two explanations why urban workers may prove to be more productive than their rural counterparts and, therefore, command higher wages. Also, why would less-educated workers in highly-skilled cities earn more than their counterparts in less-educated cities? Be sure to site particular sources of urban agglomeration economies..