Repeated Commodity Trade Strategy

[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]

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.

[Carolus Rex]

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

Carolus

[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.

[Adam Smith]

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

[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.

[David James]

And here are the answers, and they are quite surprising. I had not expected this. If the commodity is not demanded, then the bonus is the same, whether it is hides or uranium. But when several commodities are demanded, it is the ones to the bottom right of the list that yield the highest returns. So if a city demands gold and dye, and your city can supply gold and dye, send in the gold because it is the more valuable of the two. Also, and I was wrong to assume otherwise, supplying a demand always yields a greater return than not doing so.

One difficulty I have always had was deciding which foreign city to trade with. Obviously, I want one that has a lot of inherent trade in order to get the biggest returns. Short of wasting reems of diplomats, or using the cheat menu, I can only guess by looking at the population of a city and the surrounding terrain. But the AI is notorious for favouring food over all else, so even those factors can be misleading, especially very early on. If a city has a well-developed road infrastructure, its probably got a fair bit of trade. Republican governments help as well of course. So, Adam Smith, how do you decide which foreign cities to go for?

[David James]

Adam Smith,
I think we all now know that the commodities at the bottom right of the trade supply/demand chart (Uranium, Oil, Gold, etc) yield greater returns than those at the top left (Hides, etc). We also know that fulfilling a demand nets a greater benefit than not, right? But what if the demand is near the top left of the chart? Might you be better off disregarding a low-return demand and instead supplying a higher return commodity? Have you ever tried this and do you know the modifiers for each commodity and whether or not demand is fulfilled?

That's a lot of questions. It just seemed unlikely to me that supplying the demand of hides could possibly yield a greater return than sending in oil or gold. Of course, I am assuming the same two cities, same base trade, etc. The only difference is the commodity. Maybe I will try this out using the cheat menu. Just that if you already know than I can save myself the time.

[jpk]

Thanks for the trading advice. I was playing as Gauss Chancellor of Germany and repeatedly shipped freight unit after freight unit of hides to the Persian capitol. I had a few cities that could produce hides turn after turn. While it lasted (perhaps 20 turns) I was making 1200 coins per turn from the hides. I had two cities on the same continent as the Persian capitol and another on a nearby island. All three cities had airports so transportation was not a problem.

[David James]

Uranium seems to be very rare and short-lived. I've had it disappear whilst building a freight unit. Also, placing a single worker in a sea square often alters the trading commodities. Not always, but often. I noticed this when I removed my only sea worker once. At any rate, Civ2 does some pretty weird things in the trade department.

[aarrdd]

Adam Smith: I have noticed that some cities don't change their commodities demands and after sending lots of the same commodity to one of these cities, one of the commodities that city supplied changed to Uranium. This was the first time I ever had a city which supplied Uranium and I attributed to this the fact that I kept on supplying with the commodity it always demanded.
Could this be true?
Do you know another way in which a city can supply Uranium?

[Adam Smith]

Matthew:
Your post on the Wonders thread brought this back to mind. I have some trade formulas from one of the guide books, but we pretty much established on the Two Continents thread that those formulas were incorrect in some instances. Xin Yu supposedly worked out the correct formulas through experimentation. He was going to post them on Stewart Spink's web site, but I dont know if he ever did.

[David James]

Matthew,
One method to test continents is to right click on a square on a land mass. The display at the right will give you the x-y coordinates as well as another number. This is what I call the continent number, because it changes from continent to continent (the main ocean is '1' I believe, and inland seas and lakes also have different numbers). From this you will be able to tell if two continents are actually two continents.

For science flask overflows, I'm not sure that you do get the overflow. In the early stages of one game, I counted them each turn and especially when a discovery came about. I may have been very fortunate to always have the right amount because there was never any overflow. Next game, I'll take a look again.

One strategy that I employ with trade routes is to find the biggest, most trade productive city in the rest of the world (usually a Babylonian city). I send a caravan from as many of my cities as possible to this city (if I can fulfill a commodity, fine. If not, so be it) in order to establish as many rich trade routes as possible. Yet they only benefit from 3 of them and I from 20+. Sometimes I find the 2nd and 3rd biggest as well, but I usually choose to trade domestically because I get the benefit at both ends.

[Matthew]

On a similar note, is distance in the equasion for the trade bonus modified for smaller maps? Also, if somebody could post again the equasion for trade bonuses that was on the deleted two continents trade strategy I would appreciate it. And what exactly constitutes a continent? I know that any time you have to cross water you go to a different continent, but what about two enormous land masses conected by only one or two land squares? And what about the ice caps, or land only connected by the ice caps?

[Matthew]

I noticed this, but thought that It might be because I was homing the caravans to another city. This won't work as well in MP, where I hear you can't re home caravans, but It could still be quite useful.