Repeated Commodity Trade Strategy

[Adam Smith]

aarrdd:
I will be the first to admit that I have no idea what causes cities to arbitrarily change the commodities they supply and demand. Some changes appear to be technology related. For example, cities usually start supplying oil about the time you get industrialization, though in my current game I have a city that supplied oil as soon as I got trade, about 1000 bc. Oil usually starts to get demanded about the time of the automobile, though I have tried giving civs automobile in order to generate demand for my product, and that does not always work. Similarly, my impression is that uranium starts to be supplied sometime before nuclear fission, and starts to be demanded shortly after that. Is there a uranium resource square? Could that have something to do with it?

David James I:
According to a manual I have, commodity bonuses are paid for the following commodities, in decreasing order (commodities on the same line are supposed to have the same bonus)
Uranium
Oil
Gold, Silk, Spice, Gems
Silver, Wine, Cloth
All Other Commodities: No commodity bonus.
This is slightly different than the "lower left-upper right" order, but I have never checked it out, and you may well be correct.

The commodity bonus does not seem to matter as much as I thought it would. In the game I am currently playing, I completed a silk trade route for $754, and on the same turn cheated up another trade route between the same two cities involving something low-valued that was also demanded. I wound up getting $682 for that, which was much more than I expected. The difference between high and low valued commodities does not appear to be much.

David James II:
I usually select cities to trade with first by size. I will sometimes refine my assessment by looking at the terrain, especially roads and special resources. As far as government, I wont bother trading with anybody in monarchy or despotism, unless its their capital and its pretty big. Usually its got to be republic or better to open.

[Adam Smith]

PS: Xin Yu and Ming did some testing on these sorts of issues, and may be able to shed some light.

[David James]

Adam Smith,
The manual that you refer to isn't the manual that came with Civ2, right? Anyway, all commodities that are demanded get an additional bonus. Even lowly hides came in at over 2 times the standard bonus. I picked up the formula from a post by Enur over a year ago somewhere else and it checks out for the standard bonus. But I don't know the commodity modifiers. Anyway, courtesy of Enur (a direct quote of him) from a manual he bought here is the formula for the initial bonus:

"Base bonus=((distancex+10)x(source trade+destination trade))/24.
[diagonal square distance = 1.5, "normal" = 1]
[Source and destination trade are the trade before other trade routes, less corruption, I believe]

Bonus modified for demand=base bonusxFD, where FD depends on demand fulfilled or
not (example, Oil:FD=1.5.)

Bonus modified for civ=
(Base Bonusx2)+Demand bonus (if the city belongs to your civ.)
Bonus modified for civ=
(Base bonus+demand bonus)x2 (if the city is alien.)

And now finally, pay attention:
During the first 200 game turns, or until Navigation and Invention have been discovered:
Final bonus=Bonus modifiedx2.

After the discovery of railroad: Final bonus=bonus modifiedx0.67.

After the discovery of flight: Final bonus=bonus modifiedx0.33.

Because 2/0.67=3, this explains why Xin Yu experienced the drop to 1/3. It must have
been after the discovery of railroad. If it was after the discovery of Navigation and
Invention, it would only be reduced to 1/2."

Square brackets [] are mine. You can see that Xin Yu was already up to his tricks of testing things out. The reason I wanted to know about commodity modifiers is because they are counted so early in the equation that back figuring is quite tedious. Again quoting Enur, this time for the permanent bonus:

"Trade icons=(source trade+destination trade+4)/8. (half of the trade goes to each city)

Modifiers:
-Both cities are yours: -50%.
-Freight unit: +50%.
-Cities are connected by a road: +50%.
-Cities are connected by a railroad: +50%.
-Both cities have airports: +50%.
-Cities are on different continents: +100%.
-[Source] city has superhighways: +50%. [affects each city individually, though trade
increase from having will increase route trade slightly]

The bonus is explained earlier. These modifiers therefore apply only to the trade icons generated, not to the bonus. And fulfilling demand doesn't increase the trade icons, only the bonus. Distance doesn't affect trade icons, only the bonus."

Interesting, isn't it? Distance has no effect, nor does fulfilling demand, on the permanent bonus. The Civ2 manual is very poorly written in this area, because there is an implication that they do have an effect. I really wish that all the formulas for everything were in the manual. It would make things so much easier for us.

[Carolus Rex]

Yes, but then interesting threads like this one wouldn't exist :-)

Carolus

[Adam Smith]

David James:
You are correct: the actual Civ II manual is pretty near worthless for this type of stuff. The formulas you posted look the same as those in David Ellis' Civ II: The Official Strategy Guide. However, I think it had been established on a previous thread that some of these trade formulas are incorrect. This may be due to errors in the book or to unspecified changes that were made to the trade fromulas in V2.42 (I think). For example, I think that one of the changes had to do with the idea that airports add 50 percent to the value of a trade route, so that two airports increase the value by 100 percent.

Now, a question:
I have heard that trade formulas are adjusted for the size of the board. For example, a trade route that covers one quarter of the distance on the small board will have the same bonus as a trade route that covers on quarter of the distance on a large board, regardless of the distance actually covered on either route. Anybody know for sure? This is really important if trying to play for a fast finish on a small board.

[Matthew]

Also the initial trade bonus for freight is +50%, at least with a forign civ on the same continent. I will have to do some experimenting to figure out exactly how freight figures into the equasion. Also it seems that the first half of the trade comodities have the same modification factor for fulfilling a demand.

[Adam Smith]

I just saw the week-old references to the "Crummy Tech" trading strategy and the "Two Continents" trading strategy. Thanks for the recognition, though some clearly goes to Xin Yu. I thought I would dig this thread up and give it a bump because subsequent play has shown that this strategy is even more productive than the "Two Continents" strategy. With a super science city, six or eight other small cities to support, and no tribute or alliances I can usually finish a Deity game (land on AC) about 1780. With creative use of tribute I am sure it can be done by 1750 or sooner.

[Adam Smith]

Bump.

[MyOlde]

Thanks for the Bump.

[don Don]

*Bump!*

[Adam Smith]

Bump.
Subsequent play has shown that you dont need to rehome caravans to make this strategy work well.
This thread does not appear to be in the archives. Should it be?


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[Sten Sture]

On a vaguely related issue - if you do have a repeating supply commodity and send it twice to the same city you do NOT set up an additional trade route if the demand is already fulfilled. How does this work with a repeating demand commodity?

Is that clearly worded??

[Ribannah]

If a city wants say Silk and has turned (Silk) after delivery, the demand will be renewed after delivering another, this time non-Silk caravan.

Changes in demand mainly occur after (1) certain tech discoveries and (2) city growth.
City growth can also renew the old demand.

Continued demand after delivery happens in cities with a large amount of trade (makes sense, right?). But I've never seen it happen to my own cities, only the AI's.

- Rib -

[tonic]

I think the supply aspect is relevant seeing it's trade strategy. One related question for me is what determines the reappearance of commodity caravans/freight after its initial exhaustion and after you've built x number of food caravans?

I came across a commodity-supply pair loop in my OCC12 game. As long as I sent the caravan to the target city, Paris, I could alternate the Gold and Wine caravans indefinitely it seemed. Unfortunately both commodities were not in demand but nevertheless at that stage of the game each did generate a bonus of 217 gold and a corresponding small science bonus (imposed Fundy government in the game).

In testing the saved games later I found that interrupting this alternating supply loop eg by sending the Gold caravan to another city that demanded it, broke the supply loop ie only food caravans could be built after that!

[Sten Sture]

Rib are you sure about your first point; that would imply - if I am thinking straight - that no city would have two items in parens at one time. I have seen that quite often...