Four to five weeks of vacation is pretty standard in Europe and I don't think it has anything to do with productivity. AFAIK, a German or Belgian would pretty much get the same amount of vacation. I'm in Montreal and the standard by law here is two weeks but my contract with a local employer is giving me four weeks. And, I'm still working when I'm working, even if I have some vacation time at some point?!

I took eight weeks this year. So you're saying I (or a French person?) am not getting anything done when I work, because I took some extended vacation time?