Resource Field Efficiency Guide

Hey guys, I am going to throw out some information about resource field efficiency. 
Note: There is a ton of information in this article, if you trust me to give you the best, and most efficient way to upgrade your resources fields, just read the bold parts. If you don't believe what is written in bold, you should read the rest.

I have found that many players do not understand the idea behind field efficiency (which is critical when Sim City-ing.) I don't mean that this is only useful for non-aggressive players; even big farmers build up their fields at some point. So let's get started. 
Please take note that these numbers will be different depending on if you are using gold, and whether you are on a speed server or not, but for comparison sake, all of the numbers will be the same. (eg. If one field pays itself off in 2 days and one pays off in 3 days, that ratio will be the same regardless of what server you are on or whether you use gold or not (given that you use gold for both resources, of course.)) Okay, now that I have thoroughly confused half of you and bored the other half, let's move on to the meat of the article.
I see many people, even very experienced players, that build their bonus buildings much earlier than is economically feasible. For example, it does not make sense to build all level 1 crop fields and then build one to level 5 so you can get the grain mill, it takes too many resources and the payoff just isn't there. Likewise, it is not feasible to build all level 5 clay pits and then get one to level 10 so you can get a brickyard, you are wasting resources. The best way to build them, from my experience and number crunching (I graduated with a Math degree, for what it's worth), is the following:

Crop Fields: Build all to levels 5,5,6,6,6,6, build grain mill level 1. All to level 6, grain mill level 2. All to level 7, grain mill level 3. All to level 8, grain mill level 4-5. One to level 10, Bakery to level 2. All to level 9, bakery level 3. All to level 10. The last 2 bakery upgrades are actually less efficient than building a level 10 residence, building 3 settlers, founding a new village, and building all of your fields up to level 8 (your crop fields actually make it back faster than bakery level 4 and 5 do.) The only reason to build further bakery upgrades is if you are short on CP and have all level 10 fields in all of your villages. I will not include the math here, because it would take up half the article.

Clay Pit: All to level 7. One to level 10, Brickyard to level 3. All to level 8, Brickyard to level 4. All to level 9, brickyard to level 5. All to level 10. This is the same for Woodcutters and Iron Mines.

I know most of you think this is all garbage, so I will include my calculations.

Crop level 1: 250 resources, 3 (9) production increase (payoff in 3.47 days)
Crop level 2: 415 resources, 4 (12) production increase (payoff in 4.32 days)
Crop level 3: 695 resources, 6 (18 ) production increase (payoff in 4.83 days)
Crop level 4: 1165 resources, 7 (21) production increase (payoff in 6.93 days)
Crop level 5: 1945 resources, 11 (33) production increase (payoff in 7.37 days)
Crop level 6: 3250 resources, 17 (51) production increase (payoff in 7.97 days)
Crop level 7: 5425 resources, 20 (60) production increase (payoff in 11.30 days)
Crop level 8: 9055 resources, 30 (90) production increase (payoff in 12.58 days)
Crop level 9: 15125 resources, 45 (135) production increase (payoff in 14.00 days)
Crop level 10: 25255 resources, 55 (165) production increase (payoff in 19.13 days)

Above level 10:
level 11: resource production - 280
level 12: resource production - 375
level 13: resource production - 495
level 14: resource production - 635
level 15: resource production - 800
level 16: resource production - 1000
level 17: resource production - 1300
level 18: resource production - 1600
level 19: resource production - 2000 (requires over 10 level 20 warehouses to build)
level 20: resource production - 2450
level 21: resource production - 3050
level 22: resource production - 3750
level 23: resource production - 4600
level 24: resource production - 5650
level 25: resource production - 6950 (requires over 22 level 20 warehouses to build)


The numbers for production that are in parenthesis are for a speed server. The payoff values are for a normal server, just divide by 3 to get speed server values. I didn't want to waste any more space on that list.

The first thing I want you to notice is that every subsequent level is less efficient than the previous. I have been a sitter on multiple accounts where they build one field to level 10, then move to the next one. That is a terrible way to operate. As you can see from the information so far, the best way to upgrade fields is by getting them all to level 1, then all to level 2, and so on. But that is not where things get confusing. The tough part is when you add in the bonus buildings.

Okay let's start with the Grain mill.
Grain Mill level 1: 2560 resources, 5% bonus.
Grain Mill level 2: 4605 resources, 5% bonus.
Grain Mill level 3: 8295 resources, 5% bonus.
Grain Mill level 4: 14925 resources, 5% bonus.
Grain Mill level 5: 26875 resources, 5% bonus.

With 5 level 1s and 1 level 5, you produce 63 resources. A 5% bonus gives you 3 wheat.
Would you rather pay 2560 for 3 wheat per hour, or 415 for 4 wheat per hour. That's an easy one.

With 5 level 2s and 1 level 5, you produce 78 resources. A 5% bonus gives you 4 wheat.
2560 for 4, or 695 for 6? Easy

With 5 level 3s and 1 level 5, you produce 108 resources. A 5% bonus gives you 5 wheat.
2560 for 5, or 1165 for 7.......

With 5 level 4s and 1 level 5, you produce 143 resources. A 5% bonus gives you 7 wheat.
2560 for 7, or 1945 for 11.....still cheaper

At all level 5s, you produce 198 wheat per hour. 5% of that is 10 wheat.
2560 for 10, or 3250 for 17. The first one pays itself off in 256 hours. The second one takes less than 200 hours. The normal wheat field is still more efficient. It actually becomes more efficient to build a grain mill after about 4 fields are upgraded to 6. I will spare you the math.

Okay let's move on to the other fields. I will use the clay pit as the example.
Clay Pit level 1: 250 resources, 3 (9) production increase (payoff in 3.47 days)
Clay Pit level 2: 420 resources, 4 (12) production increase (payoff in 4.38 days)
Clay Pit level 3: 700 resources, 6 (18 ) production increase (payoff in 4.86 days)
Clay Pit level 4: 1170 resources, 7 (21) production increase (payoff in 6.96 days)
Clay Pit level 5: 1940 resources, 11 (33) production increase (payoff in 7.35 days)
Clay Pit level 6: 3250 resources, 17 (51) production increase (payoff in 7.97 days)
Clay Pit level 7: 5425 resources, 20 (60) production increase (payoff in 11.30 days)
Clay Pit level 8: 9060 resources, 30 (90) production increase (payoff in 12.58 days)
Clay Pit level 9: 15125 resources, 45 (135) production increase (payoff in 14.00 days)
Clay Pit level 10: 25250 resources, 55 (165) production increase (payoff in 19.13 days)

The clay pit, and the other two resource fields, are all very close in price to the wheat field. Thus, their payoff rates are very similar.

I hope by now I have your trust that my calculations are accurate, so I am not going to include as much detail this time around. 

At level 7s, with one level 10, your clay production is 410 per hour. If you upgrade your brickyard you will gain 22 clay production. If you upgrade another clay pit to level 8, you gain 30 clay per hour. 
Level 1 brickyard: 1290 resources, 22 clay.
Level 8 clay pit: 9060 resources, 30 clay.

I show you these number first because at a glance it looks like an easy answer. The problem is, you should not have 7,7,7,10 when you make this decision, you have 7,7,7,7 We have to include the cost of the clay pit we upgrade from 7-10. So what we are really comparing is a clay pit from 7-8, or a clay pit from 7-10 plus a brickyard build. 

Clay pit from 7-10 + brickyard to level 3: 57220 resources, 193 resources per hour (296 hours)
Clay pit from 7-8: 9060 resources, 30 clay per hour. (Payoff in 302 hours)

Notice that it is actually much closer than you would have thought, but it is more efficient to go 7,7,7,10 +3. The 4th and 5th upgrade of the brickyard should not be done until later, since they take 358 hours and 645 hour to pay themselves off at this level. You should upgrade the fields to all 8s before doing level 4, and all 9s before doing level 5. This pattern fits for both woodcutters and iron mines as well.