http://i.imgur.com/g9NA76s.png
An extra 5% of working age employment in the US would mean something like 7M more jobs.
The more important question is, how are similar countries that didn't adopt the 35 hour week doing?
We could also make the argument that cutting taxes would spur more spending. If you increase my disposable income, I'll buy some new studio monitors and an Allen & Heath mixer.
Just increasing vacation time results in a higher labor cost and thus raises prices, negating the benefit.
If you include intangibles like quality healthcare and reasonable amounts of vacation time, then I'd argue that France is far wealthier than the US.
I guarantee if you asked Americans if they would trade their 2.5% (or whatever) economic growth for Germany's 1% in exchange for 20 days guaranteed vacation per year, most would say "hell yes". The people who wouldn't take the trade are those rich enough to not need the vacation.
Not me, I'm going to buy some expensive speakers
Who'd have thunk.
Not gonna buy a boat for 10 vacation days total per year.. Why would I?
25 days on the other hand.. That's a solid three extra weeks of boating. Might buy a boat.