Modeling economics (first of many parts)

In Sundog (the game), there were 30 types of cargo that could be transported by the pod (and thus by the ship), plus nothing and cryogens (the ‘green ice’ pods) — 32 types in all (because, binary). Each had an associated base price. Here’s the data from the original game, with the base price for each cargo type:

code cargo price
0 nothing 0
1 ship’s fuel 20
2 radioactives 193
3 gems/crystals 176
4 rare earths 201
5 exotic metals 175
6 gold 123
7 antimatter 243
8 grains/cereals 25
9 fruits/vegs 44
10 woods/fibers 15
11 seeds/sprouts 37
12 meats 67
13 stock embryos 77
14 spices/herbs 69
15 organics 71
16 chronographs 110
17 silichips 134
18 biochips 179
19 cadcams 153
20 synthesizers 146
21 sunsuns 134
22 comgear 169
23 nullgravs 199
24 droids 222
25 pharmaceutical 114
26 clothing 93
27 weapons 174
28 furs/silks 200
29 art objects 220
30 stimulants 255
31 cryogens 0

This is actually not a bad list to consider in Frasgird, at least to start with. The names are generic, suggestive and mostly understandable (“sunsuns” were portable fusion power units for home and industrial use).

The actual buying or selling price for a given cargo type on an actual exchange in a specific city on a specific planet in a specific system depended upon several additional factors. These included:

  • A supply-and-demand factor that represented how much you had bought or sold of that type of cargo there recently (the factor reset to normal over a period of weeks). Each and every city had its own supply-and-demand table; the more often you bought a particular cargo in a particular city, the more expensive it got, and then it just wouldn’t show up in the marketplace for a while; likewise, selling the same cargo in the same city too often depressed the prices significantly. The bottom line was you couldn’t set up a profitable ‘milk run’ by shuttling between two cities on the same planet.
  • The ‘wealth’ factor of the planet, a value in the range 0..15 that represented the general income level/standard of living of the planet.
  • The ‘quality’ of the cargo, rated A..H (7..0), with ‘A’ (7) being highest.
  • For certain ‘tech’ cargos (16..24 in the list above), the ‘tech’ factor of the planet.
  • Whether you were buying at the (sole) spaceport on a given planet or whether you were buying at one of the other cities on that planet (25% bonus for selling, 20% discout for buying at a non-spaceport city).
  • Whether you were selling a specific load of cargo in the same city, on the same planet, or in the same system where you bought it. (Yes, each cargo load ‘knew’ where it had been bought.)
  • Whether you were selling the cargo to the colony-under-construction (they would pay a premium price for it — this was done mostly to reduce the grindingness of the game).

All this was implemented with a relatively small section of code, all using integer math (8-bit 6502 processor). But it was highly effective. I knew of players who used a second personal computer to keep track of the prices for goods in all visited cities.

However, Frasgird introduces a number of differences. For starters, the dominant sapient populations are alien, not human, and certain cargoes (such as food, clothing, etc.) would tend to be species-specific. Since different worlds will have different types and sizes of alien populations on them, it makes trading in general more complex but also more interesting. Likewise, cross-species trading would readily occur for many other cargo types, particularly for areas of specialization and expertise. And even than could vary. Alien art from a particular species might be highly prized by other species, but perhaps only on certain worlds or even just in certain cities.

More later.

Filed Under: EconomicsModelingTrading

About the Author

Webster has been doing game design since 1980, but only has one actual published game to his credit -- Sundog: Frozen Legacy (Apple II, 1984; Atari ST, 1985). This is his second.

Comments (2)

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  1. Chris says:

    Boy, that “base price” table sure would’ve been handy with SunDog. I had no idea whether I was paying (or getting) a high or low price for a commodity!

    • Heh. I knew of people who used spreadsheets or database programs running on a separate computer to try to keep track of prices in different cities.

      [Added later] On the other hand, one of Jerry Pournelle’s criticisms of Sundog (and a valid one) is that the player should have access to technology at least as advanced as the computer the player is playing on. Our problem in Sundog was the very tight limit on RAM and disk space, but he’s right: you shouldn’t have to write down stuff. In Frasgird, you are going to start out with a lot of information, and that will get updated as you have characters you are interacting with or controlling return from visiting various systems. What you can’t count on is how well that information will hold up between successive visits, or after a quantum jitter.

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