In my recent game I had problems with food, and with problems I mean that I was getting too much of it (really too much, compared to toher civs); note that this game is based from a revision of the SVN around the 5th of december (I never upgrade in the middle of a game because it will screw up and unbalance things), so I hope nothin has changed in this time
As you can see form pic #1, on turn 1230 I am in the renaissance era and one of my city has reached size 120 (for comparison, the best city of the AI is "only" size 80); so I asked myself how I could have such a big city
In pic #2 you can see the answer: trade routes. They cause more or less 90% of the food produced in my city, which is really really a lot. I then decided to investigate to see how I could produce all that food.
My city has 14 trade routes, each with a base profit varying from 5.6 to 4 gold; the gold produced gets then converted into food, with the proportion 1
1.3 
; since I'm running a civic that increases food from trade routes by 30%, I suppose the base ratio is 1:1.
In pic #1 are listed the modifiers for trade routes the most important of which is the population: every population point above 10, is a 5% increase to the trade route income (so for size 120 it is (120-10)*0.05=5.5=550%). Since population is so important, I asked myself how a pop increase modifies the trade route income: doing some calculations with an excel file (it is in the zip I attached) I saw that at size 121 the trade route produced 5,78 more than at size 120.
This means that the more your city grows, the more food it produces and so the more faster it will grow; since every population consumes 3 food, there is 2,78 food of surplus that accelerates the growth of the city. This seems strange to me because I think that population can't grow indefinitely, but it shoud tend to a fixed value.
POSSIBLE SOLUTION: I redid the calculations using a ratio 1:0,1 between commerce and food; the food produced was 127.43, more or less the same as the food produced by buildings and tiles together. I think that this way the trade routes are still important, but you have to take care also of buildings and tiles (actually, if you have similar trade routes you can avoid working tiles, using population points only for specialists)
In the zip file I put the savegame and a copy of the excel file
As you can see form pic #1, on turn 1230 I am in the renaissance era and one of my city has reached size 120 (for comparison, the best city of the AI is "only" size 80); so I asked myself how I could have such a big city
In pic #2 you can see the answer: trade routes. They cause more or less 90% of the food produced in my city, which is really really a lot. I then decided to investigate to see how I could produce all that food.
My city has 14 trade routes, each with a base profit varying from 5.6 to 4 gold; the gold produced gets then converted into food, with the proportion 1
1.3 ; since I'm running a civic that increases food from trade routes by 30%, I suppose the base ratio is 1:1. In pic #1 are listed the modifiers for trade routes the most important of which is the population: every population point above 10, is a 5% increase to the trade route income (so for size 120 it is (120-10)*0.05=5.5=550%). Since population is so important, I asked myself how a pop increase modifies the trade route income: doing some calculations with an excel file (it is in the zip I attached) I saw that at size 121 the trade route produced 5,78
more than at size 120.This means that the more your city grows, the more food it produces and so the more faster it will grow; since every population consumes 3 food, there is 2,78 food of surplus that accelerates the growth of the city. This seems strange to me because I think that population can't grow indefinitely, but it shoud tend to a fixed value.
POSSIBLE SOLUTION: I redid the calculations using a ratio 1:0,1 between commerce and food; the food produced was 127.43, more or less the same as the food produced by buildings and tiles together. I think that this way the trade routes are still important, but you have to take care also of buildings and tiles (actually, if you have similar trade routes you can avoid working tiles, using population points only for specialists)
In the zip file I put the savegame and a copy of the excel file
