Economics

The registered systems of skcomplex.systems.economics. The page of each shows its factory, its component types with their states, parameters, and laws as written, and, for the forms that have them, its equations as SymbolicAnalysis returns them, so it serves as the pattern for a system of your own.

Econophysics

• Boltzmann wealth exchange: A Boltzmann wealth exchange system where every agent starts with one unit.
• El Farol: Arthur's El Farol bar problem, whose attendance self-organizes around the capacity.
• El Farol with strategic group formation: Collins' El Farol bar with strategic group formation, whose coalitions share their best strategy.
• Exchange with debt limit and with saving propensity: A kinetic wealth exchange system with a saving propensity or a debt limit.
• Kinetic wealth and welfare dynamics: The kinetic theory of wealth classes, with a welfare policy when the tax is positive.
• Kolkata Paise Restaurant: The Kolkata Paise Restaurant problem, where diners spread over restaurants that serve one meal each.
• Minority game and its evolutionary version: The minority game of an odd number of agents with two random strategies each.

Finance

• Bouchaud-Mézard wealth: Bouchaud and Mezard's wealth dynamics, random multiplicative returns with exchange between neighbours.
• Correlated geometric Brownian motions: Two assets whose prices follow geometric Brownian motions driven by correlated Wiener processes.
• DebtRank cascades: The DebtRank cascade of distress from a set of banks through their interbank loans.
• Default cascades with thresholds and recovery: A cascade of defaults through interbank exposures, from a shock to the external assets of some banks.
• Eisenberg-Noe clearing of interbank payments: The clearing of interbank payments of Eisenberg and Noe, a fixed point of proportional payments.
• Fire sales of overlapping portfolios: Banks with overlapping portfolios whose fire sales of common assets spread their losses to one another.
• Fundamentalists and chartists in an order book: A stock market of fundamentalists and chartists on a grid who trade in a limit order book and imitate.
• Geometric Brownian motion: An asset whose price follows geometric Brownian motion.
• Gibrat: Firms that grow by Gibrat's law of proportionate effect, which makes their sizes lognormal.
• Kesten processes: Firms whose sizes follow Kesten's process, a random multiplicative factor plus a random positive term.
• Kirman exchange rate with switching traders: Kirman's foreign exchange market, whose traders switch between fundamentalism and chartism like ants.
• Multiplicative: Levy and Solomon's multiplicative process, whose floor at a fraction of the mean makes a power-law tail.
• Order book with a guru communication network: The order-driven market of Grilli and Tedeschi, whose noise traders imitate gurus they choose by wealth.
• Random-walk traders with arbitrage: Schwichtenberg's diffusion of a good by random-walk traders, minimally coupled to exchange rates.
• Traders and exchange rates coupled through arbitrage as lattice electrodynamics: Exchange-rate potentials on links as lattice Maxwell fields, sourced by traders who move a good on sites.

Innovation

• Arthur-Polak technology evolution: Arthur and Polak's evolution of technology, which builds logic functions from NAND gates.
• Bass diffusion: The Bass diffusion system, people who adopt a new product through advertising and word of mouth.
• Co-evolving combinatorial critical model: The co-evolving combinatorial critical model, whose diversity shows punctuated equilibria.
• Combinatorial creative phase transition: The diversity of a combinatorial system, which jumps from sparse to full above a critical rule density.
• Fixed-line phone adoption: Hamill and Gilbert's adoption of fixed-line phones by British households from 1951.
• Interacting urns with triggering on a network: One urn with triggering per node of a network, which draws from its own urn and those of its neighbours.
• NK technology system: McNerney's system of technological improvement, whose cost falls as a power of the cumulative production.
• TAP growth with random catalysis and autocatalytic sets: The TAP growth of goods from combinations of goods, with random catalysis of their production functions.

Macroeconomics

• Brock-Mirman stochastic growth: The Brock-Mirman economy, the optimal growth of a representative agent whose productivity is Markov.
• Capital stock: Meadows' capital stock, grown by reinvested output and drained by depreciation.
• Exchange rates in international trade: Hamill and Gilbert's staged adjustment of trade and the exchange rate to a rise in home prices.
• Firm and bank credit networks: A credit market where firms sample banks and switch to cheaper lenders, and defaults hit the lenders.
• Fractional-reserve banking: Customers and banks whose lending of excess reserves multiplies the base money by 1 / ratio.
• Linear network herding: Agents whose linear choices herd on the past choices of the agents they are linked to.
• Mark-0 economy with a Covid shock and policies: The Mark-0 economy of Sharma, Bouchaud, and co-authors, with a Covid shock to supply and demand.
• Metaphoria mortal hunter-gatherer and monetary economies: Gooding's Metaphoria, a mortal population of hunter-gatherers or of a monetary economy.
• Multiplier-accelerator: Samuelson's multiplier-accelerator, Y_{t+1} = c (1 + v) Y_t - c v Y_{t-1} + G.
• Pontryagin capital and consumption: The Ramsey economy that chooses the consumption path maximising its discounted utility.
• Solow: An economy whose capital per worker approaches its steady state through saving and depreciation.
• Stock-flow consistent monetary economy: A stock-flow consistent economy, a closed circuit of money between households, firms, and a bank.
• Three-sector purchasing power decoupled by feedback: Forrest's categorized purchasing power of money, three sectors that feedback can steer one by one.
• Toy firm investment: Heterogeneous firms that invest out of past profits and sell at random prices, with entry and exit.

Markets

• Beer distribution game: Sterman's beer distribution game, a supply chain whose orders swing wider at every echelon upstream.
• Bilateral barter of two or three goods: Traders who wander a grid and barter two or three goods with their neighbours.
• Bilateral two-good trade on complete, isolated, and small-world networks: Wilhite's bilateral barter of two goods among traders on one of four trade networks.
• Brock-Hommes heuristic switching: Brock and Hommes' asset market with traders switching between fundamentalists and trend chasers.
• Car wash queue: Chesney's Clean and Wax hand car wash, a shadow account of the revenue of its workers' labour.
• Car-dealer inventory with delays: Meadows' car dealership, whose inventory oscillates after a step in demand because of its delays.
• Cobweb: A market whose price converges to or oscillates around equilibrium as supply lags the price.
• Commodity cycle with capacity delay: A commodity market whose price and capacity cycle because new capacity arrives after a delay.
• Cournot duopoly with beliefs: Two Cournot duopolists that adjust their output to their beliefs about each other.
• Customers choosing between two shops of perishable goods: Customers who choose between two shops of perishable goods, preferring the one that sold fresher goods.
• Edgeworth and Red Cross barter: Barter of chocolate and cigarettes, in an Edgeworth box of two barterers or among many prisoners.
• Fair Food Program: Chesney's Fair Food Program, in which pressure on tomato buyers draws farms into fair wages.
• Fair-trade food choice with peer influence: The choice between fair-trade and regular food of consumers who influence their neighbours.
• Gooding double auction with adaptive quotes: Gooding's double auction, whose buyers and sellers move their quotes towards trade and then apart.
• Heterogeneous household demand by utility and by elasticities: Hamill and Gilbert's heterogeneous households, whose demand for food traces a curve as its price rises.
• Labour market: Hamill and Gilbert's labour market of firms posting wage offers and unemployed workers searching.
• Produce market: Hamill and Gilbert's produce market, where shoppers with lists of produce visit stalls at random.
• Riccati price adjustment: A price that moves with excess demand under linear demand and saturating quadratic supply.
• Shops and digital markets: Shops on a grid that compete for the shoppers on every cell, in person or in a digital market.
• Static oligopoly equilibria: The equilibria of a Cournot duopoly and of a pricing game of firms with loyal customers and switchers.
• Sugarscape: The Sugarscape of Epstein and Axtell, foragers of random vision and metabolism on two sugar peaks.
• Toy Trader and Three-Goods Trader with money: Gooding's Toy Trader, traders with money and toys who buy the cheapest toy they can see.
• Zero-intelligence double auction: Gode and Sunder's double auction of zero-intelligence traders, a step per trading period.

Resources

• Cocoa: A cocoa production system, plantations that boom with their profit and bust with the insects they invite.
• Crop livestock household: Bala's crop livestock model, a farming household that adds livestock rearing to its crop income.
• Fishery with measurement errors: Independent fisheries whose quota is set from a measurement of the stock with a Gaussian error.
• Food security systems: A food security system, the rice self-sufficiency of a country under subsidy, research, and extension.
• Harvesting farmers: A socio-ecological system of farmer agents harvesting a logistically regrowing resource.
• Hilsa fishery: A hilsa fishery, the life cycle of a migratory fish that the catch of juveniles and spawners depletes.
• Oil economy: Meadows' oil economy, capital that grows on a nonrenewable resource and collapses as it runs out.
• Optimal harvesting: A logistic resource harvested with the effort that maximises its discounted profit.
• Renewable fishery with capital: Meadows' fishing fleet, capital that grows on a renewable resource and can overshoot it.
• Rice land, population, and food security: Bala's food security model, rice land that grows towards the land available against a growing population.
• Tragedy of the meadow commons: Herders whose cows graze a shared meadow, each adding cows while a cow pays, until the grass collapses.
• Von Thünen land use: A square plain around one market at its centre, whose every cell grows the crop of highest bid rent.