 The literature on happiness has surged in the last decade. The findings are well summarized in many surveys (see in particular Diener (1994, 2000), Diener et al. (1999), Frey and Stutzer (2002), Graham (2009), Kahneman et al. (1999), Kahneman and Krueger (2006), Layard (2005), Oswald (1997), Van Praag and Ferrer-i-Carbonell 2008), and reveal the main factors of happiness: personal temperament, health, social connections (in particular being married and employed). The impact of material wealth is debated, some arguing that it is more a matter of relative position than of absolute comfort, at least above a minimal level of affluence (Easterlin 1995, Clark et al. 2008), others arguing that there is a positive (but logarithmic: doubling income induces a constant increment on happiness) impact over the whole range of observed living standards (Deaton 2008, Sacks et al. 2010) .