Monopoli Azionario
A board game as a test bench: markets, institutions and money simulated seriously enough that you can be wrong inside them.
The evening the table had to print money
Third game, turn forty-something. The Government owes a coupon and has no cash: the payment does not happen, it becomes an arrear, and a referendum opens on screen. The table has to decide whether to authorise the creation of money.
Whoever holds no bonds votes no on instinct: why hand purchasing power to a government that spent badly? Then they notice a line at the bottom of the screen: while it stays in default, the Government pays five basis points of risk premium for every turn of arrears, and that premium enters the ladder of every auction that follows. Which means: a no pushes rates up for everyone, and whoever bought bonds — quite possibly the person voting no — watches their capital lose value.
Nobody wrote that dilemma as a rule. It fell out of the interlocking of a public balance sheet, an auction and a yield curve. That is exactly why this project exists.
Not Monopoly with a few extra rules
It is a financial market simulator on a Monopoly board, with a coherent macroeconomic system sitting on top of the board game. The difference shows up in a single question: how much of that shop did you buy?
Ownership is fractional. You do not buy the shop, you buy 10% of it, or 30%, or 60% — and everything else follows from there. "Not buying" stops being an event and becomes a continuous state: there is always a piece left on the market, always contestable.
Above the board live a Government with a profit and loss account and a balance sheet, a Central Bank that creates and destroys money, a yield curve formed at auction, a price index, a tax with an automatic adjustment rule, and a technical default you only escape through a vote of the table.
And there is one invariant holding it all together:
Σ players' cash + Government cash + Central Bank cash
= initial money + money created + monetisations
Verified to the euro, discrepancy 0.000000. Every euro that appears has a name: it comes from a mortgage, from a Central Bank purchase, or from a printing run authorised by the table. Everything else is a transfer. That discipline is what makes the macro credible rather than decorative: in a game where squares burn cash, the economy deflates by itself and inflation becomes a fiction.
The share, and what follows from it
This is where the market comes from: shares are sold only between players, on the board or through private negotiation, and there is no buyer of last resort. Whoever needs cash and finds no buyer has no comfortable way out: they take a mortgage, pledge collateral, and risk foreclosure. The tension of the game lives there, in liquidity, not in the dice.
The rate is not computed: it is observed
This is the part I am proudest of, and the one that surprises first-time players. No formula sets the rates. Every turn the Government posts a bell-shaped ladder of €100 tranches centred on the current rate; players buy from the highest yield down; the yield of the last tranche allocated becomes the rate, and it moves immediately, inside the purchase.
Equilibrium sits at mid-ladder. Thin demand → the marginal stays high → the Government pays more. Demand that absorbs everything → the marginal drops → it pays less.
The Government places new funding needs on whichever maturity is cheapest at that moment, so the curve moves on its own. The fifth maturity — the five-turn policy point — is reserved for the Central Bank: players see it, they cannot buy it. When the Central Bank buys, the Government raises cash without draining the players, its funding need falls, it issues less paper and yields come down by themselves: transmission is through the market, not by decree.
Calibrating all of this was the real work. A flat distribution instead of the bell pushed the marginal up 190 basis points in twenty-five rounds; an automatic increase on every failed auction took the curve from 0.55% to 2.70%; using the highest yield sold instead of the marginal one meant +10 bp for every auction that sells, forever. Every parameter that looks arbitrary is the scar of a measurement that went wrong.
The Government: a balance sheet, not a cash machine
The Government collects sales tax, rent on the shares it has not placed yet, and interest on mortgages; it pays the GO bonus, welfare and coupons. Issuing bonds is not revenue: it is funding, and keeping the two apart is what stops a government borrowing to pay salaries from looking healthy.
Out of that balance sheet come four signals — funding need, leverage, coverage of financial charges, average debt maturity — and a fiscal rule that moves the tax rate inside a band, slowly: frozen for the first thirty turns, then one adjustment every fifteen at most.
Then there are seven guaranteed commitments (the GO bonus, coupons, redemptions at maturity, repayment to the Central Bank, citizen's income, the disability subsidy, buying back a bond a player sells). Miss even one and the default I described at the start opens up. Public works and new property placements, by contrast, are discretionary: no cash, no works.
The Central Bank: three options and a ceiling
It operates only on the short maturity and can do three things: roll its holdings (money unchanged), let them mature (money withdrawn, parked on its own account), subscribe new tranches (money injected). It spends the cash it has already withdrawn first, and only then creates: new money is the last resort.
It reacts to the gap between inflation and its own norm — a thirty-turn average, with a half-point dead band — under a ceiling of 20% of the money stock that is enforced, not merely displayed: above the ceiling it stops rolling, exactly as in a tightening. And the card states plainly the distinction that usually gets lost: how much money was created out of nothing and how much was withdrawn and is sitting there. Two different things, and on this table you can see which is which.
What you can actually do, beyond rolling dice
Insure a square. It is a digital option: it pays the notional if the insured player lands on that square within T turns. The probability is not estimated: it comes from a 40-state Markov chain with the square made absorbing, validated independently in Python and in JavaScript, including the jail teleport and the probabilistic branch of the shortcuts. Two properties fall out on their own: one square has probability zero and cannot be insured, and Jail is the most expensive cover on the board, because the teleport makes it an attractor. The clock that matters runs from roll to roll, not from turn to turn.
Borrow. Mortgages over four maturities, each priced off its own point on the curve times a spread. One mortgage can carry many pledges, each with its own LTV — bonds 90%, receivables 80%, shares 70%, crypto 60% — and if an instalment goes unpaid foreclosure happens in minimum lots: the Government takes just enough to cover the instalment, not the whole loan, and the mortgage continues on the remaining collateral.
And then: symmetric private negotiation (I offer / I ask, with counter-offers), player-to-player loans, neighbourhood shares that discount profits net of tax, crypto and milk quotas tradable only in whole units, five characters whose abilities genuinely change strategy (the Banker borrows with no spread, the Builder pays 20% less on investments, the Lucky One re-rolls at a doubling price after seeing the square), the Flash Market that opens when you pass through Jail in transit, and the neighbourhood monopoly that doubles rents — market power that generates measured inflation, and generates it by itself.
Watching an economy while it happens
There are no numbers hidden by the bank. The yield curve, the price index, the Government's accounts, the Central Bank's portfolio are all on the table, and all of them are consequences of what the players did. When inflation rises it is not because a script decided so: it is because someone assembled a neighbourhood monopoly, or because the table voted to print.
That is what makes the project more interesting than the game itself. A macro model read in a book stays abstract; here the same dynamic lands on you while you are trying to win, with other people pulling in different directions. You understand sooner, and better, why a central bank does not "decide" a rate, why a risk premium gets paid even when it feels unfair, and why liquidity matters more than net worth.
How it is built
A single HTML file — engine, interface and data inside — of about eighteen thousand lines, living in two ways: locally, by opening the file, and online in synchronous multiplayer at monopoly.micheleferramola.com, with invite-based tables, a collaborative setup room, private player-to-player chat and automatic reconnection. The server keeps an authoritative copy of the game per table and runs the same page as the client: browsers send intents, receive the state, and redraw only the zones that actually changed.