Battle-for-Tismo/shared/data/economy.js

// National economy constants and the pure formulas the server and the browser
// both use to derive production, training time, budget income and population
// growth.

// Trade taxes are the government's only revenue; there is no GDP-based tax.
// Every region buying from another region inside the country pays a national
// sales tax on top of the price. A foreign buyer pays an export tariff to the
// seller's government, and a region buying from abroad pays an import tariff to
// its own government on the national currency it spent acquiring the foreign
// currency. Rates are per nation and may be overridden per resource.
export const TAXES = {
  defaultSales: 0.2,
  defaultExport: 0.05,
  defaultImport: 0.05,
  // The highest rate a player may set, per kind and resource.
  maxRate: 1.0,
  // The three tax kinds, in the order the panels list them.
  kinds: ["sales", "export", "import"],
};

// The buckets the monthly budget report groups a nation's spending into. Each
// row carries a signed cash movement (positive is money into the treasury) and,
// for the upkeep rows, the market value of the materials consumed whether they
// were drawn from stores or bought. `group` is the heading the table files the
// row under.
export const BUDGET_EXPENSE_CATEGORIES = [
  { id: "buildings", label: "Building upkeep", group: "Upkeep" },
  { id: "units", label: "Unit upkeep", group: "Upkeep" },
  { id: "works", label: "Tile works", group: "Upkeep" },
  { id: "transport", label: "Transport", group: "Upkeep" },
  { id: "campaign", label: "Campaign", group: "Government" },
  { id: "construction", label: "Construction", group: "Investment" },
  { id: "training", label: "Training", group: "Investment" },
  { id: "tilebuild", label: "Tile improvements", group: "Investment" },
  { id: "provisioning", label: "Provisioning", group: "Resources" },
  { id: "energy", label: "Power", group: "Resources" },
  { id: "military", label: "Military supplies", group: "Resources" },
];

// The monetary system: each nation issues its own currency and runs a central
// bank. Regions are the private sector, each holding a basket of currencies.
// When their cash runs out they borrow from the central bank, and the same bank
// lets the government run an overdraft. The interest rate is the cost of that
// borrowing, not a direct lever on inflation.
export const MONEY = {
  // The central bank's opening lending rate, charged on every debt each year,
  // and the ceiling a player may set.
  defaultInterestRate: 0.02,
  maxInterestRate: 0.5,
  // Private-sector cash a region opens with, as a share of its yearly GDP.
  privateCashFraction: 0.5,
  // Each day a region converts this share of every foreign holding back into its
  // own currency.
  repatriationPerDay: 0.05,
  // How much a currency's value may move from par, either way.
  maxRateDrift: 0.9,
  // How hard a day's net foreign demand pushes a currency's value.
  demandSensitivity: 0.5,
  // When several regions chase the same scarce surplus, each further buyer
  // raises the price it pays by this share, capped at `maxBidMultiplier`.
  bidPremium: 0.3,
  maxBidMultiplier: 2,
  // The central bank's foreign-exchange desk. It works the reserves the nation
  // earned abroad: it retires the national money foreign banks hold, sells more
  // reserves to defend a weak rate, and pays part of the nation's foreign
  // purchases out of reserves to keep food and energy imports cheap.
  fx: {
    // Share of the bank's foreign reserves spent redeeming the national money
    // held abroad on an ordinary day.
    redemptionPerDay: 0.004,
    // Extra share sold on a day the national currency sits below `weakBelow`.
    interventionPerDay: 0.05,
    // The value against par the bank treats as a weak rate to defend.
    weakBelow: 0.98,
    // The share of a foreign purchase of each resource the bank covers from its
    // reserves, and the most of its reserves it will spend subsidising imports
    // in one day.
    importSubsidy: { food: 0.5, energy: 0.5, steel: 0.25, luxury: 0, hightech: 0.25 },
    importSubsidyPerDay: 0.02,
  },
};

export const ECONOMY = {
  basePopulation: 100_000,
  cityTileProductionMultiplier: 2.0,
  capitalTileProductionMultiplier: 2.5,
  citySurroundingProductionBonus: 0.3,
  gdpPerProductionPoint: 100_000,
  // Building and tile-improvement construction runs this much faster than
  // training: a building takes a tenth of the hours a unit of the same cost
  // would. Unit training is untouched.
  buildingTimeMultiplier: 0.1,
  // A nation opens the game on 1 January 2000 with a tenth of its starting GDP.
  startingBudgetFraction: 0.1,
  startingBudget: 1_000_000_000,
  basePopulationGrowthRate: 0.005,
  // Natural growth of production: every day a tile gains this share of the
  // production it opened the game with. The amount is constant, so the relative
  // growth rate naturally tapers off as the years pass.
  naturalProductionGrowthPerDay: 0.0001,

  productionCapacity(gdp) {
    if (this.gdpPerProductionPoint <= 0) return 0;
    return gdp / this.gdpPerProductionPoint;
  },

  trainingHours(gdp, cost) {
    const capacity = this.productionCapacity(gdp);
    if (capacity <= 0) return 0;
    return cost / capacity;
  },

  // The hours a building or tile improvement of `cost` takes to rise, ten times
  // quicker than training something of the same cost.
  buildingHours(gdp, cost) {
    return this.trainingHours(gdp, cost) * this.buildingTimeMultiplier;
  },

  populationGrowthFactor(hoursPerYear, hours = 1) {
    if (this.basePopulationGrowthRate <= 0 || hoursPerYear <= 0 || hours <= 0) return 0;
    return Math.pow(1 + this.basePopulationGrowthRate, hours / hoursPerYear) - 1;
  },
};