How do you THINK you'd increase the population? BUILD FLATS. If the faction in control has built more flats that you can conceive, then they have ensured their control well. If they own 100% of the cities on the planet, then they have ensured their control well. If they are a government, and they arrest every construction NPC you place on the planet, then they are doing their job well.
Do you have any questions about control that can't be answered with a quick reading of the rules, a few moments' thought and a little common sense?
Oh, there was that question about the price of planets. Go look in the Traders Lounge. There was a thread on that same subject a little while back. 3-6 months ago, maybe? I'm pretty sure it was less than a year, at the most.
____________"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."
Only fools and children dream of heroes.