Get Thee To a Nunnery

From my medieval economic history classes I was taught that convents were a form of population control: in the absence of a sufficient dowry, a particular clan would pack some of its hapless daughters off to a nunnery, so that it does not burden the clan economically, as well as lowering the overall fertility rate of that particular extended household.

George Duby adds some additional exposition:

The fact that Ernaud d'Echauffour's two daughters were relegated to a convent signals a decline of this branch of the family and its exclusion from the political contest in Normandy

The context here is that daughters were important strategic tools that can be "deployed" so as to maximize the total prestige and security of a household (this is medieval Europe; Tina Turner comes much later). Conversely, being forced to send your daughters to a convent is a signal that there is low "demand" for associating with your clan.

This make me wonder if sending your daughter to a convent ever became a self-reinforcing process:

• You were forced to send your oldest daughter to a convent because of short decline in your political/economic fortunes
• Everyone sees that your send your oldest daughter to a convent, reducing their expected strategic payoff via a marriage to your second daughter.
• Facing a lower demand for your second daughter's hand, you are to forced to send her off to a convent, further isolating your own household strategically
• ...And so on

If this kind of dynamics did indeed exist, then a short-term travail (bad harvest in your domain, for example) can lead to long term malaise, even if there is nothing inherently wrong with this particular aristocratic household. It depends how intensely 11th century Normandy nobility played to this signal...