A couple of questions regarding Independents

[Vanguard_DW]

At what point will a independent world become a empire? is it population based, development level or sheer randomness?
Secondly is the population growth rate for independents wad?

I ask because in a game I was wrapping up 30years or so in (in view of moving to 1.0.6), I noticed the three eyed rat things were about to colonise a ind Kiadian world, one of its resources was Loros fruit and its pop was 14billion! It's population growth rate was 14%

I never really paid much attention to the independent growth rates before but most of them are around the 13% to 14% mark no matter how high their population, I normally colonise/acquire independents soon as pos, but even planets with half a billion population don't help that much at the beginning with your home planet providing most of your income. Therefore I'm going to try and leave a couple planets close to home independent and was wondering if there's a point I should move in before they become a major player.

Also wondered if anyone else has tried this tactic? For a short term cashflow loss it should lead to a large long term gain.

[Shark7]

Some will, some never will.

Generally they need a population of over 1 billion, a decent amount of planet development, and you'll probably notice a lot of independant cargo ships hanging around the planet...that seems to be a good indicator that it is ready to turn into an empire.

It also depends on the species stats...extremely stupid species (like the Atuuk or Teekan) will likely not turn into an independant empire.

[the1sean]

Shark7 put it very well, and if I remember correctly those rats arent a smart race, so even though they had high population they never made the leap to sovereignty.