“…This evidence is usually explained by differences in human capital stocks, as firstly suggested by Nelson and Phelps (1966), and/or by institutional quality heterogeneity, (Hall and Jones, 1999;Acemoglu et al, 2001and 2006, Comin et al, 2009, and/or by the existence of monopoly rights of various forms that create a barrier to technology adoption, as in Parente and Prescott (1999). However, more puzzling is the evidence that slow processes of technology adoption are observed even across similar leading countries of the world economy (Comin andHobijn, 2004 andComin et al 2006) or across regions within the same country or within union of states (see Magrini, 2004, for a review).…”