**Trade (cont)**

**2.6.12 Predicting Commodity Supply and Demand Lists**

Using Samson’s formulas, it is possible to predict what the supply and demand lists will be for any city at any time in the game. Since these formulas are complicated, and because there is a need to calculate two quotients for each commodity each time a list is updated, it’s difficult to justify the time and effort required to do all of this. Plus, there are so many variables at work in determining the values of commodity supply and demand, it would not be surprising to find out that one or more of the formulas are incomplete or partially incorrect. In fact, while working on this section, I think I uncovered a new problem with the formula for the demand of spice. This will be discussed a little later when illustrating calculations.

Thus, the use of these formulas may be limited to the most important cities such as the SSC, where a more precise understanding of the ebb and flow of supplies and demands may be desired. Rome, which was the SSC used in my first comparison game, will be used to illustrate the use of these formulas. Rome’s wildcards were figured out in the previous section, and the save attached there named “wild” will also apply here.

Before getting into the calculations for Rome, a few words about Civ II geography might be helpful, so that players using Samson’s formulas will not make any errant assumptions that might throw off the accuracy of their calculations. Civ II has an option to use small, medium and large maps, and each tile for all maps is assigned a horizontal and vertical map coordinate. The zero horizontal coordinate (or zero meridian) corresponds to the International Date Line of our Earth, which makes Civ II’s mean meridian correspond to the Prime Meridian of Earth, so it is important not to confuse Civ II’s zero meridian with Earth’s zero longitudes. Less confusing are Civ II’s vertical coordinates, which start with zero at the North Pole and reach their maximum at the South Pole.

For each of the standard map sizes (small, medium and large) used by Civ II, here are the key statistics:

**Horizontal Map Coordinates (east and west)**

Number of Coordinates (Map Width) 80, 100, 150

Range 0-79, 0-99, 0-149

Zero Meridian 0, 0, 0

Mean Meridian 40, 50, 75

Range of Western Longitudes 1-39, 1-49, 1-74

Range of Eastern Longitudes 41-79, 51-99, 76-149

**Vertical Map Coordinates (north and south)**

Number of Coordinates (Map Height) 50, 80, 120

Range 0-49, 0-79, 0-119

North Pole 0, 0, 0

Northern Polar Circle 8, 13, 20

Northern Temperate Zone 12, 20, 30

The Equator 25, 40, 60

Southern Temperate Zone 37, 60, 90

Southern Polar Circle 41, 66, 100

South Pole 49, 79, 119

Any distances required for Samson’s formulas will always end up being positive numbers. Since some of the horizontal calculations may be a bit confusing here are a few examples to go by (MC will be used as an abbreviation for the Civ II Horizontal Map Coordinates):

Small Map Examples

MC 31 is in the Western Hemisphere and its Longitude is 9 (40-31)

MC 77 is in the Eastern Hemisphere and its Longitude is 37 (77-40)

The Distance to the Mean Meridian for MC 31 is also 9 (40-31)

The Distance to the Mean Meridian for MC 77 is also 37 (77-40)

The Distance to the Dateline for MC 31 is 31 (31-0)

The Distance to the Dateline for MC 77 is 3 (80-77)

Medium Map Examples

MC 31 is in the Western Hemisphere and its Longitude is 19 (50-31)

MC 77 is in the Eastern Hemisphere and its Longitude is 27 (77-50)

The Distance to the Mean Meridian for MC 31 is also 19 (50-31)

The Distance to the Mean Meridian for MC 77 is also 27 (77-50)

The Distance to the Dateline for MC 31 is 31 (31-0)

The Distance to the Dateline for MC 77 is 23 (100-77)

Large Map Examples

MC 31 is in the Western Hemisphere and its Longitude is 44 (75-31)

MC 77 is in the Eastern Hemisphere and its Longitude is 2 (77-75)

The Distance to the Mean Meridian for MC 31 is also 44 (75-31)

The Distance to the Mean Meridian for MC 77 is also 2 (77-75)

The Distance to the Dateline for MC 31 is 31 (31-0)

The Distance to the Dateline for MC 77 is 73 (150-77)

With these preliminaries out of the way we can load up the save “wild” and inspect Rome. A right click on the city reveals its map coordinates which are (18,12). From the last section we already know that the wildcards for Rome are, so let’s continue by counting up the terrain features in Rome needed for the calculations:

Ocean = 9 + 2 fish = 17

Grassland = 4

Plains = 3

Hills = 1 + 2 wine = 9

Rivers = 3

Roads = 6

Land = 10

Note that each fish counts as 4 ocean and each wine counts as 4 hills, and that the Land count ignores the extra amounts provided by specials. Rivers are counted in addition to their underlying terrain. From the save we can also collect the rest of the information we will need for the making the calculations:

Tech total is 32 (31 plus the one being learned)

Known techs affecting commodities: Iron Working, Chemistry, and Economics

Improvements affecting commodities: aqueduct, marketplace and bank

Number of citizens in Rome: 21

Continent Number: 1 (displayed to the right of Rome’s map coordinates)

City Number: 1 (from “Find City” list, Rome is first)

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