Do you know where/what the formula is? My mars colonists are growing very unhappy, and i kinda need to know. Heh.
If you look on the summary screen for the colony, it will have an entry for infrastructure. The line below that is supported population. So if your pop is higher than that, you need to relocate some citizens or increase the infrastructure.
As for the formula, I did a brief search of the mechanics forums (which I thought it was in), but did not find it.