France surpassing the USA in hourly productivity makes sense intuitively if you think about how the statistical series are composed. Hourly productivity is output divided by hours worked. The result varies inversely with the size of the denominator.
The problem with conventional political economy, both mainstream and heterodox, is the implicit assumption that maximizing aggregate output is, for all intents and purposes, equivalent to optimizing it. The assumption simplifies things radically and facilitates all sorts of seemingly profound econometric analyses.
Not only are maximizing and optimizing not equivalents, in many circumstances the maxima are suboptimal in the extreme. Think of obesity or alcohol consumption, for example. Composition is more important than quantity.
The output per hour figures are consequently more significant than the output per person figures. Still more significant would be a breakdown of the output per hour into life enhancing versus destructive and/or restorative output (the Genuine Progress Indicator angle).
The entire process can be greatly simplified by applying the maxim that "wealth is disposable time." (see http://www.vcn.bc.ca/timework/dispose.htm). In that anonymously published phrase can be found the inspiration for Marx's development of the concept of labour power, as distinct from labour. I suspect also that the central argument in the anonymous 1821 pamphlet was also, in turn, influenced by a book on public happiness by the 18th century French immortal Chastellux. The happiness in question would be of a type that one might pursue, as in "life, liberty and the pursuit of happiness."
So, maybe if the French are doing it better than the USAnians it's because it was their idea in the first place. By the way, there is an ironic episode in Adam Smith's Theory of Moral Sentiments in which he depicts the pursuit of leisure as leading to a 'happy' excess of industriousness, suggesting, perhaps that vicarious sloth is the invisible hand that guides the overachiever.
Tom Walker Bowen Island, BC 604 947 2213