(However, if one holds some old fashion notion that a 'job' constitutes 40h payed wage labour each week, the 'jobs' would presumably be fewer. I cannot see why or how one would advocate for this, though.)
The lump of labour or lump of jobs fallacy is an argument generally considered to be fallacious that the amount of work available to labourers is fixed. Contending that the amount of work is flexible not static, most economists oppose such arguments. Another way to say this is that it treats a quantity as if it were an exogenous variable, when it's not. It may also be called the fallacy of labour scarcity, or the zero-sum fallacy, from its ties to the zero-sum game.
And I kinda doubt the fallacy, with the way UK and France have about the same amount of hours worked ; the greater UK work participation rate due to, well, shorter weeks on average. Auferre, trucidare, rapere, falsis nominibus imperium; atque, ubi solitudinem faciunt, pacem appellant.
