I admit that I have significant holes in knowledge regading the "Middle Ages in the Mediterranean" region of space-time. I am biased towards the NW region of Europe partly because there's a wealth of material accessible to me pertaining to the area, partly because I derive most of my income from providing language services for the language spoken in the region, and therefore I am expected to have more than just a passing familiarity with this region's culture and history (although I am partially excused from having to know it to any significant depth as I specialize mostly in technical and engineering texts where this knowledge isn't all that important, and history is merely my part-time hobby). I haven't seen a general work dedicated to the Romance-speaking and Mediterranean regions either in English or in my native tongue yet, therefore I plead incompetent on this charge. :-)

I might, however, try to dig up some data pertaining to my native, i.e., Central European environment; however, not on such a short notice for it to be relevant to this discussion.

EDIT: I wonder about the tradeoffs involved here. Tentative hypothesis: in Northern climates, the labor of daughters was more valuable, so fathers kept them around for longer before marrying them off.

My take on this - I believe that some of the factors involved were:

- the necessity for young people to help their families work on the household,

- the necessity for young women to earn their dowry, if their families couldn't provide it for them (usually by entering into service of nobles or townsmen for a few years),

- the stagnation of land development outside periods of borderland colonization (different periods in various countries, in Central Europe, this period of colonization would have taken place between 11th and 13th century), meaning that someone had to retire first for another pair of young people to get their household.

I'm quite sure there would have been other reasons that I can't recall right now.