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How Supply and Demand Lists Are Determined

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  • #16
    Any and all,

    I've posted the formulas for Hides to the placeholder spot above. I'm looking for feedback on the format in which to present them. Is this clear and understandable?

    The first line is the terrain-based part of the formula. Although not all commodities use terrain, the vast majority do. The lines that follow terrain are other factors that affect the S/D calculations: location, techs and # of techs, city size, etc. Not every formula uses every factor, but I thought presenting them in a common format would make comparisons easier.

    Like I said, I want feedback before moving ahead with this. Even those who have no intention of ever calculating S/D lists can learn something about how Trade works if the data is presented clearly, I think. All comments are welcome.


    • #17
      The format is very clear and looks good to me.

      If hides are typical, there are many factors to calculate for each commodity in each city, making it likely that only a few players will end up doing this. However, just a glance at the formulas can tell you in a more precise way of trends that can be expected and if a site is likely to produce or demand hides, which to me, will make all the formulae quite useful.

      Keep them coming, please!

      Back to wildcards, for a moment, where I have a question about one city, Nineveh (43,33), which has a supply wildcard of copper and a demand wildcard of hides. So far, there has been one change:

      2200 s: hides,copper,salt d: dye,wool,silk
      1550 s: beads,salt,wine d: dye,hides,silk

      The only explanation I can see for not having copper on the supply list in 1550, is that it moved to the demand list, underneath hides. If this is the case, it seems like quite a wide shift from where it was in 2200. The only event of note to happen in the city in the meantime, was that I built a temple. Did the temple give copper enough of a boost in its DQ to end up 2nd on the demand list? Or is there some other factor I am missing here?

      (Note: the Babs learned Astronomy & Navigation during this interval, but I don't see them listed above as affecting copper.)
      Last edited by solo; November 16, 2002, 16:22.


      • #18
        OK, this is fascinating! Cold places seem to want hides... So far it looks like a group of programmers got together over a couple bags of Cheez Pops and tried to describe real world demand and supply of hides in game parameters. This paradigm may help in guessing future formulas, but I suspect Samson is already trying that.

        I still don't see any mention of the special aspect of hides - namely that its supply never seems to appear as (Hides), and often is not listed as the Trade Route from the source city. Could there be a factor which reduces a commodity's SQ if it is currently supplied to another city? That might be part of an explanation for the repeating of some commodities on supply lists, especially if it is subtractive not multiplicative.

        And on the subject of the Dye bug, a silly thought - is it possible that it may be an inverse side effect of the set of parameters which make Uranium supply so rare? Or is Uranium (which can never be a wild card according to these formulas) just given such unlikely SQ parameters that it will always be rare? In any case, the scarcity of Uranium is unusually effective in most games, either by a programmer's mistake or as his pride and joy.


        • #19
          Excellent study! I spent a fair amount of thought on doing something similar, but never got up the nerve to put together such a time consuming test. Hats off to samson!

          I feel especially good for having speculated that map location was the prime determinant of commodity availability, particularly after reading:
          There are two Wildcard commodities, one for supply and one for demand. These are based solely on the city's map coordinates.
          Thanks, samson, for the effort.
          The first President of the first Apolyton Democracy Game (CivII, that is)

          The gift of speech is given to many,
          intelligence to few.


          • #20
            Grigor -

            OK, this is fascinating! Cold places seem to want hides...
            Yeah, and the places that supply Hides are Forest and Tundra (where "Game" is found) and Rivers and Jungle where furry animals abound. Small trading posts (city size 1 or 2) have 2X modifiers for both supply and demand.

            I think the formulas do tell a story. Take a look at Beads, posted above.

            Could there be a factor which reduces a commodity's SQ if it is currently supplied to another city?
            Possibly. There are several formulae I haven't been able to crack yet. But Hides is close to correct, I think, with nothing in its formula to explain its unique property.

            The scarcity of Uranium is probably caused by having a extremely high DQ relative to its SQ, which means that it only rarely shows up the Supply list.


            • #21
              Marquis -

              You're very welcome. And yes, your suggestion about location was one of the things I tested, proving fruitful not only in the wildcard notion, but also in geographic concepts as well: proximity to poles or equator, etc. In fact, I think all of the ideas people have suggested here have turned out somewhere in my testing to being valid.


              • #22
                First, here's a hunch I've always had that you probably can not make any use out of! I've always suspected that irrigation of hills causes more wine to appear on S/D lists.

                I have gone back and checked many situations where hides has either gone off or come on lists in my hot seat test game, and there is a strong correlation with the hides formulae.

                When Trade was shared with all civs, there was a lot of tech gifting that causing almost every civ to loose their 4x multipliers in the tech department for both supply and demand. Hides on supply lists even slipped further as cities started growing past size 2. In my MGE game, hides are definitely following the expected trends predicted by the hides formulae.

                Even more convincing is the fact, that in cases where hides have been added to supply and demand lists, this has often happened because of their status as wildcards in cities where this has happened!

                There were also 3 cases where it appeared that hides were added to demand lists, when this actually may not have happened. In all three, it looked very likely that they had just remained on lists, having moved out of the middle position where they had been previously covered by a wildcard. In two out of three cases, hides might have actually lost status by moving down to the third position on the demand lists.

                So with hides, the current trend towards having less on both lists has become even more noticeable and predictable. It is encouraging news that quotients and wildcards work for both the 2.42 and MGE versions of the game.

                The depth of insight and proficiency with which Samson has been able to unravel the mysteries behind these lists sometimes leaves me wondering whether or not he has a copy of the Civ II source code.
                Last edited by solo; November 16, 2002, 16:12.


                • #23
                  >Wool: Supply = (Grass + Hills x 2 + Rivers/2 ) x (Tundra + Glacier + 2)

                  Are you sure about this Wool Supply formula? The multiplication of Tundra + Glacier seems strange.

                  The Cheez Puffs theory might go this way: Wool comes from sheep and goats (and llamas which we will ignore) which grow in, like, England, so grass and hills are good, and rivers make it extra green so they are sort of good (?) plus it's extra thick wool if it's real cold, which for some reason we will measure by tundra and glacier squares instead of distance from the equator.

                  >Demand = Plains x 2 + Forest
                  >Location: + TemperateZoneOffset x 2
                  >Techs: Industrialization: 2x

                  The Demand side is harder to figure - let's see: only plains and forest count because everything else is either too comfortable for wool or too severe for wool (or else grows their own) and this demand gets greater as we move to the Tropics (Our Man in Havana) or to the poles (Ragg socks). But with industrialization, we can make Nylon.

                  I am not totally following this logic.


                  • #24
                    Originally posted by solo
                    I've always suspected that irrigation of hills causes more wine to appear on S/D lists.
                    I've tested irrigation, mining, and roads but have found no correlation to any commodity S/D changes so far. I thought at one point that roads were a factor but that data proved suspect and I have discarded the notion.

                    Originally posted by solo It is encouraging news that quotients and wildcards work for both the 2.42 and MGE versions of the game.
                    Yes it is. And much thanks again for the independent testing you are doing on MGE and the confirmation of these findings. This project is much tougher than the work I did with caravan delivery payments. There the payment numbers were known and thus the derived formula could be tested for correctness. In this case, the entire model and even the existence of DQs and SQs is supposition; an hypothesized mechanism for explaining the Supply/Demand phenomenon. So there is nothing to check correctness against except the same behaviors from which the model was derived. However, correspondence of the model to the actual design is not necessary, as long as its predictions are close enough to fact to be useful.

                    ... sometimes leaves me wondering whether or not he has a copy of the Civ II source code.
                    No, not hardly. I will say this though, this project has given me a real appreciation for the depth of thought and intelligence in the game's design. Perhaps, I'm reading too much into it, but it seems to me that the Trade system attempts to simulate the historical importance of different trading commodities to civilizations and eras with an understated humor and elegance.


                    • #25
                      Originally posted by Grigor
                      Are you sure about this Wool Supply formula? The multiplication of Tundra + Glacier seems strange.
                      ... I am not totally following this logic.
                      The formulas are empirically derived; correspondence, or lack of it, to historical or economic reality is an interesting result not a contradiction or confirmation. I like the Beads formula because it reflects the distribution of seashells from which beads were made. But the formulas I present here are simply what I've found and I don't understand all the logic of them either. I do understand the increase in demand for Wool caused by Industrialization though. The cloth mills of England is where the Industrial Revolution got its start.


                      • #26
                        Yes, the design of this game never ceases to impress, especially the parts dealing with trade.

                        I have some news about dye on my pattern thread that shows more conformance by MGE with 2.42. This is good news.

                        When you have enough commodities finished, I'm looking forward to checking them against what really happened in my MGE game.

                        Also, I'm hoping that I'll be able to block all supplies in that game fairly soon to see the effects this might have on the whole trading system. With all civs building and delivering caravans, supplies are starting to disappear rapidly.


                        • #27
                          I've updated the formulas list above with all my latest results. TBD means "to be determined". A note on testing methodology. All factors have been tested singly, that is by changing only that factor and holding others constant. There may be factors that interact to produce effects only when combined. The problem is too complex to test for all such possibilities.


                          • #28
                            I've found and added the Demand Quotient formulas for Silver, Gems, and Gold. Interestingly, these three commodities demands are interrelated. More remarkable is that the demand is based solely on the city's size. This is great as it means that there are now three demand commodities that can be easily and surely calculated. This should make the determination of other demand formulas easier. It also should allow more rigorous testing of existing formulas and the underlying model of the trade system.


                            • #29
                              I'm stumped by the complexity you are finding, but it is clever. So the system can tell the difference between the Chinese and any other civ regarding Silk? I thought it only knew the CivNumber. In one of my recent games all the Japanese cities demanded Silk for a while. Guess that was just a fluke.

                              Some of these Location formulas, it can all be expressed mathematically using the map size and the city location. But it helps us understand logically the way you relate it to the zones and lines you do. Good work. Now for some serious testing...

                              Practically speaking, we're all wondering how we can use this to make a city that Supplies Uranium consistently...


                              • #30

                                Yes, there will be lots of testing to do. I'm sure the formulas have flaws in them, and perhaps the model will need to be rethought, too. Anyone who wants to help, can. Just check the S/D lists of some cities during gameplay against the predictions of the model and formulas and report the results. If they don't matchup post a save and I'll look into it.

                                As for Uranium, I've posted its formulas above. The reason for Uranium's scarcity is apparent. Uranium's supply is terrain based and scaled by city size. But Uranium's demand is based an the square of the number of Techs acquired. It, too, is scaled by city size, but faster than supply. In a typical game, Nuclear Fission is discover rather late, by which time the player has 50 or more techs. This creates an enormously high demand quotient which the supply side equation can never match. Thus U is always demanded, not supplied.

                                To supply Uranium, you need to steal or trade for Nuclear Fission while you are still far behind in the tech race. This would give you a low enough demand quotient in cities with the appropriate terrain to be able to supply Uranium. Alternatively, you could give NF to a low-tech civ, wait for some of their cities to start supplying Uranium and then conquer them. I don't believe that conquering a city triggers S/D list changes. So you would have until that city's next solo-cycle year to build Uranium caravans.

                                Some of my testing suggests that Uranium may, like Oil, also be a secondary Wildcard. If that proves true, then there may be another way of getting a city to supply Uranium.