The idea - economists would call it the lump of labour fallacy - the idea that there is just a fixed number of jobs and all you have got to do is try and divide them up between young people, old people, males, females - I think it's nonsense.
Very dangerous to ever point a finger at another European country but I sometimes think the French, with their obsession with the 35-hour working week, they are falling into the danger of a lump of labour fallacy, where ‘if only everyone just worked 35 hours there would be more work to go round.Also at Guardian Politics live blog.
"Why economists dislike a lump of labor," Tom Walker, Review of Social Economy, 2007, vol. 65, issue 3, pages 279-291
Abstract: The lump-of-labor fallacy has been called one of the “best known fallacies in economics.” It is widely cited in disparagement of policies for reducing the standard hours of work, yet the authenticity of the fallacy claim is questionable, and explanations of it are inconsistent and contradictory. This article discusses recent occurrences of the fallacy claim and investigates anomalies in the claim and its history. S.J. Chapman's coherent and formerly highly regarded theory of the hours of labor is reviewed, and it is shown how that theory could lend credence to the job-creating potentiality of shorter working time policies. It concludes that substituting a dubious fallacy claim for an authentic economic theory may have obstructed fruitful dialogue about working time and the appropriate policies for regulating it.