I mentioned this earlier in a post, but afraid nobody will response to this I repeated this again in a separate post....

As far is I see it, it is better to stick to population of 17k on big PQ planets and just built the whole planet full with Stock Market (after enough VC's are built)... This perhaps give a greater economic profit than 100k planet.....

I think this because the tax is related to squareroot of population:
1. A population of 100k have 2.4 times more tax profit than 17k population
2. A 25+ pop need at least (not counting the tax penalty) 7 VC's to keep people happy and fast growing, because to reach 100k pop takes a LONG time. This cost a lot of maintenance. To further able big pop, more and more farms are needed!
3. a 17k pop (about 50% base morale) would need at least 2 VC's and so give us 5 squares for Stock Markets! That is about 150% increase in economy and thus the tax! Then replace a VC by a stockmarket and then we have a whopping 180% increase. This is related to 2.8 times the tax profit from 17k population (more than 100k pop)!!!!! Then we still have a lot of empty spaces to fill with stock markets because no more farms are needed in contrast to 100k pop).

My Conclusion from the above mentioned scenario:
A 17k pop can have more profit than a 100k planet and is big enough for influence and planetary defense and as a supply planet for troops....

Overal conclusion:
The tax profit from a 25+ population is bad, due to squareroot formula... The formula need adaptation!!!