Thought Experiment in Population Engineering

So this is an interesting idea I've been pondering, which I figured I'd share; hopefully it's at least thought-provoking, if not amusing.

Consider this: what if there was a cheap, readily-available (as in globally) "contraceptive" pill that men could take which would deterministically set the gender of any children they would father while on said medication? For the sake of argument, we'll assume that you could get either type: male or female children. What would the effects on populations and political dynamics be, both short and long term?

For example, in areas where population is limited (either by law or by resources), and males are given better opportunity and/or status in the society, you could assume that most people would choose to have exclusively male children (especially if it would be the father who was making the choice, presumably at least sometimes without consent of the mother). Over a generation or so, this could shift the population balance significantly, which could lead to undesirable effects (eg: large populations of males without families historically are more violent). Over several generations, though, this could serve as both a population control, and a mechanism for social change, as social planners tried to make more a balanced population more appealing to the people.

In areas of gender equality, and/or where population growth is desired, you might see the opposite effect. Governments could easily encourage more females to be born through simple incentive programs, once it was easy to predetermine gender for children. Of course, this might challenge the traditional family structure within a few generations, though, as that grows out of an average gender balance, and isn't necessarily optimal in a population where gender distribution is skewed by incentives. Policy makers would have to carefully consider intentionally tipping the balance too far, for fear of unintended consequences.

In a couple generations, you might also see some interesting cross-population effects. For example, there might be more racial and area cross-breeding, if there are populations with skewed gender distributions in both directions, as people people looked outside their owns groups/areas for mates. There could also arise some power struggles and negotiations stemming from gender inequalities, and the perceived need to preserve populations (eg: it would be very difficult to preserve the strength, at least in terms of population, of a country who had 90%+ males, without drastic measures). It would have the potential to be the most significant force in gender rights equalization the world had ever seen.

Anyway, it's a thought; I'm curious what other people think.