How to have what you want: A guide to choosing the sex of your child
Let me begin by saying that this content is biased towards selecting for a male. I don't know that this is the case with all people, as I've had this conversation with a male friend sometime ago and he expressed the opposite desire, where he wanted to have 'daddy's little girl'.
In any case, a lot more evidence (under the form of studies) points to women as a determining factor, which is unfortunate as controlling certain aspects of my own life seemed lot less cold and calculated than, say, 'selecting' a mate based on the likelihood of the offspring's gender.
That being said, optimistic women ar more likely to have sons. Their expectation of how long they think they are going to live, or their perceived level of comfort and luxury is positively correlated with having sons, because having a son is more of an investment than having a daughter. For the same reason, I expect, mothers in stable relationships more likely to have boys, while single mothers are more likely to have daughters.