Click here to read Chris Colvin's excellent post on NEP-HIS Blog, where he reviews Richard Easterlin's paper ' Cross-Sections Are History '. Here is a flavour of what Chris writes in his post: Easterlin’s particular beef is with purveyors of cross-country growth regressions. He notes that studies of actual historical experience of individual countries frequently disprove expectations about causation based on cross-sectional relationships. The fact that a certain group of countries enjoys high levels of per-capita GDP and high life expectancies does not mean the former causes the latter. Indeed, the fact even that these countries were the first to enjoy both high GDP and high life expectancies still does not prove causality. Easterlin, famous for his Easterlin Hypothesis , instead argues that there could be unrelated factors causing GDP and life expectancy that cannot be picked up in a cross-sectional regression. The reason: cross sections register the results