“…Baldwin and Okubo (2006) embedded firm heterogeneity in a standard new economic geography framework in order to show that the biggest region attracts the most productive firms, 3 since these firms benefit more from backward and forward linkages in 1 There is a huge body of empirical studies on the relationship between size/density and productivity/wages including Sveikauskas (1975), Ciccone and Hall (1996), Glaeser and Mare (2001), Wheaton and Lewis (2002), Syverson (2004), Lee (2005), Wheeler (2006), Fu and Ross (2007), Combes et al (2008), and Bacolod et al (2009). For surveys, see Rosenthal and Strange (2004) and, more recently, Strange (2009).…”