I seem to recall that Grain was hard-coded to include a "population growth" effect in RTW, but that is not true in M2TW. It's a very easy test. Start up a Ptolemaioi campaign and look at the buildings in Hibis (pop 800). There's a farm with a 1% pop growth bonus and two income bonuses. That 1% growth is confirmed by the settlement details window. Don't change anything (keep the tax at "normal" which retains the full 1% pop growth) and hit end turn. On the next turn, the population is precisely 808, a 1% growth.
Now go into descr_strat (row 641) and comment out the grain resource in this province. Save the change and launch a new Ptolemaioi campaign. Look at Hibis again and everything is the same except there's only one income bonus line from the farm (because the grain resource is now absent), but the pop growth is still 1%. Hit end turn again and the T2 population is again 808. So there's no pop growth bonus from grain, either hidden or visible. You can see the same effect even more dramatically by testing Alexandria (which has 3 grain resources), but the results will be exactly the same.
There are three pips which show increases to the pop growth bar in the "settlement details" window:@Quintus, @Kull - maybe it'd be useful to change the name in 2.4 as it confuses - I suppose - also the other players? Just a thought.
- "Improvements" (house icon with grain ear)
- "Tax rate bonus" (bag of gold with green down arrow)
- "Food Import" (bag of grain with wheat ear?)
So I don't really see why "Food Import" would be more confusing than the others, especially since it uses the word "Food" in the context of "population growth".
That said, the Granary building has two different description types, one of which refers to "Food Imports" while the other talks of "Food storage" which *could be* a bit of a disconnect.
The bigger issue (to me anyway) is that the Granary uses the "population_health_bonus" and those percentages are misleading. The health bonus is given in pips in EDB, and appears on the "settlement details" screen as values of .5% per pip. Unfortunately, the building description shows each .5 percent as 5%, so (for example) the L1 Granary building says you are getting "Food Imports: 15%" when in reality you are getting a pop growth bonus of 1.5%.
Equally odd (and probably related), "Food imports" (i.e. the Granary building, or more likely the "population_health_bonus" itself) also contributes public order benefits. You can see it visible on the positive side of the "Public Order" ledger, although the building itself does not grant public order benefits (easily verifiable in EDB). Increasing the strangeness of it all, there seems to be a 2-to-1 linkage between the number of health_bonus pips and the public order benefit. So 1 pip is 0% order bonus, 2 pips are 5%, 3 pips are 10% (rounding?), 4 pips are still 10%, 5 pips are STILL 10% (no rounding?) and 6 pips are 15% (math back on track).
The whole thing makes my head hurt. :no:
Edit: Worth noting that Gigantus and I ran some tests which proved that Grain DOES have a hard-coded farm income bonus (but not a large one), so you'll get farming income from a grain resource even if there isn't a farm in the province. Also saw the same hard-code income from 1 resource as from 3, so however it works, at least it doesn't tier.