Economics is a set of machines. Here are four of them, running
Four essays where you run the model instead of reading about it: drag a curve, set a rate, hold a tournament, and the argument on the page changes with what you did.
01Why this exists
Economics is taught as a set of conclusions: taxes fall on the inelastic side, asymmetric information destroys markets, cooperation can be stable, the discount rate is a technical parameter. Each is a sentence you can be told, agree with, repeat, and never once check.
None of them is really a conclusion. Each is the output of a machine whose inputs you can change, and what matters is which settings make it say something else: a tax falls on the inelastic side until you ask how elastic and find the whole answer sits in one ratio, and cooperation is stable until you shorten the future and watch every cooperative rule in the pool die out.
You get at that by turning the dial yourself and watching which way the number moves, which is why every essay here has a working model in the middle of it rather than a picture of one.
Most of these models are wrong, in ways each essay names in its closing section. What they are good for is narrower: a model you have played with is a model you cannot be lied to about.
02The essays
Who actually pays a tax
OneTax incidence and elasticity
A parliament can decide who hands the money to the state. It cannot decide who ends up poorer: that is settled entirely by how easily each side can walk away.
You doDrag the supply and demand curves to change their slopes, set a tax per unit, switch which side the law tells to pay, and watch the burden split and the deadweight loss outgrow the tax that caused it.
Read and run itThe market for lemons
TwoAdverse selection, after Akerlof 1970
A used car market in which the seller knows what the car is and the buyer does not. Nobody lies and nobody cheats, and the market still takes itself apart, because a price that cannot tell a good car from a bad one drives the good cars out.
You doSet how far quality varies and how much of it a buyer can see, run the market round by round while the average quality and the price fall together, then switch on a warranty or a certificate and watch the market come back with a cost attached.
Read and run itThe evolution of cooperation
ThreeThe repeated prisoner's dilemma, after Axelrod
Cooperation is what survives when the shadow of the future is long enough to make betrayal expensive. Shorten the future and the same strategies, unchanged, sort themselves into the opposite order.
You doChoose the strategies, compose one of your own from four rules, set the payoff matrix and the chance the game continues, then run a round robin tournament and an evolutionary run where the successful reproduce.
Read and run itWhy the future is cheap
FourDiscounting, and the ethics inside it
The same climate damage is a catastrophe at one discount rate and a rounding error at another. The choice between them is not technical and no experiment settles it, so Stern and Nordhaus stand side by side, sourced, with no verdict.
You doBuild the rate yourself out of the three Ramsey parameters, price a damage stream at four different rates at once, and then watch the same arithmetic decide how much of a company valuation is the part nobody forecast.
Read and run it03The rules these were built under
- Run, not watchEvery model is live: what is on the page is computed while you look at it, from the settings you chose.
- Written hereEvery model is plain JavaScript with inline SVG written for these essays, with no chart library, no framework and no network call after the fonts have loaded, so each page keeps working offline.
- Sourced or cutEvery claim about the real world carries a citation with a link and the date the source was read, and attributions to named economists were verified against the source before they were written. Anything that could not be verified is not on the page.
- Limits statedEvery essay closes with what its model assumes and what it therefore cannot tell you, in the same size type as the rest. A model that does not say where it stops is being used to hide something.
- ReachableEvery interaction has a keyboard route, every model has a written summary of its current state for anyone not looking at the picture, and every figure is usable on a phone.
- ShareableThe state of every model lives in the address bar, so a link reproduces exactly the configuration the sender was looking at, down to the seed of the random draw.
04How it is built, and how to suggest an essay
One file each
Each essay is one HTML file with its styles and its model inlined, with no backend, no database, no account and no analytics, so nothing you do on these pages is recorded. The shared design system and the small library behind the models live in the same public repository as the rest of the instruments, and the build step is a shell script that splices them in.
An essay is worth building when the argument is genuinely contested or genuinely counterintuitive, when there is a model small enough to run in a browser and honest enough to be worth running, and when the sources exist to check it against. Open an issue with the argument and the source you would want it checked against.