Quote Originally Posted by Dead Moroz
Dunno if it's bug or feature. Some different farm levels have the same income value and effect on population's growth.
I don't think this is a bug, but we have no documentation to really tell us how the game is supposed to work. There are certain upgrades that don't "count" until later upgrades are done. Farming temples don't give bonuses until the farm level for that city level is completed, etc. Can't remember the details at the moment, but somebody had already figured out how it works.