Reason for subjunctive

[fglorca]

La disminución de las becas de comedor y la creciente crisis han favorecido que los padres ‘prefieran’ enviar la comida desde casa.

Why is ‘prefieran’ a subjunctive here?

[Rusty]

This is an example of cause and effect, which takes the subjunctive.
There's more said here (http://forums.tomisimo.org/showthread.php?t=2409). There's a good article linked in the thread which may help you to recognize when to use the subjunctive.