Read this if you're having problems with squlaor

[therother]

By proportional, I mean that x% pop growth does not grant x% income boost.

No, it doesn't. But here's a case study of my capital, Tarentum, at 31,739 and 50,000. (Farming income is invariant, no mines)

Taxes (low):1001/1402
Trade (1st order effects only): 6830/7427[*]
Pop Growth 0/-7%
Public Order: 120/90
Garrison: 5%/5% (~300 men stationed)

[*]I'm still investigating the effects of population on sea trading routes, specifically to do with imports (i.e. cities that choose your cities as export markets).