What a slider can do that a chalkboard can't
On the third attempt at understanding IS-LM, eight economic models that just went live, and the small bet that if you can move it, you'll remember it.
There’s a moment in every economics undergrad’s life — usually around the third week of intermediate macro — where the textbook draws two curves crossing on a graph and says, basically, “that’s the economy.” IS, LM. Phillips curves bending and twisting. The student is supposed to nod, copy the diagram, and somewhere internalize what it all means.
Most of us don’t. We memorize the shapes for the exam and forget them by the next semester. Three years later, when someone references IS-LM in a meeting at work, we nod again. And again, we don’t really know.
I had three separate attempts at IS-LM before it stuck. The version that finally worked wasn’t from a better professor. It was a moment, late at night, when I started literally moving the curves around with a pencil — push IS right, where does the equilibrium go? Push LM right, what changes? After about twenty minutes of doing that by hand, the model stopped being an abstract diagram and started being a thing. A mechanism. Something with moving parts I could feel.
That experience is the small bet behind the page that just went live at /models. Eight canonical economic models, each rebuilt as something you can grab and move. Supply and Demand. IS-LM. Phillips Curve. Solow growth. Cobb-Douglas production. The Prisoner’s Dilemma. The Laffer Curve. And, the one I was nervous about including: a pared-down DSGE/RBC model with live impulse responses.
Three sections, every time
Each model has the same shape. First, the theory — who built the thing, in what year, with what motivation, and the math in clean equations. Second, an interactive playground — sliders for every parameter that matters, charts that redraw as you move them, equilibrium dots that slide along with you. Third, classroom notes — how to actually teach the model, what students get wrong, where it breaks, what to pair it with.
That third section is the part I’m most quietly pleased with. Most online resources stop at theory and a picture. The honest pedagogical knowledge — “students often think raising the savings rate raises growth permanently; show them with the slider why it doesn’t” — almost never makes it onto the public web. It lives in lecture notes that don’t leave the classroom.
A word on DSGE
Most undergrads never see DSGE. The textbook line is that it’s “too advanced.” This is true if you mean the full Smets-Wouters paper. It is not true if you mean the chassis: a representative agent with log utility, Cobb-Douglas production, an AR(1) productivity shock, log-linearization around the steady state. With two semesters of calculus and a willingness to sit with it, an undergrad can absolutely follow what’s happening.
The playground at /models/macro/rbc-dsge won’t get you a Federal Reserve job. It will get you the intuition: a productivity shock arrives, output jumps, consumption smooths, investment spikes and collapses, capital builds slowly. Those shapes are the language of modern macro. If you’ve never watched them move, the language reads like static.
A word on misuse
These models have a history of being weaponized. The Laffer curve gets pulled out to justify tax cuts that don’t pay for themselves. The Phillips curve gets cited to argue policymakers can simply buy growth with inflation. Solow gets dragged into convergence debates that almost always skip the “conditional” in conditional convergence.
The classroom-notes section addresses this directly for each model. Not because economics should be more political — but because the political abuse of economic models is itself worth teaching. A student who graduates without understanding the elasticity of the tax base ends up unable to evaluate claims about tax cuts paying for themselves. That’s a civic problem.
Who this is for
Honestly: the version of me who was taking intermediate macro and couldn’t get the curves to feel real. But also a teacher in a Kenyan public university with thirty students, a chalk shortage, and a phone projector who would benefit from a free, polished, interactive resource. A self-taught analyst who’s read about NAIRU but never watched one shift. A journalist covering a central bank decision who wants ten minutes with the model before writing.
The playgrounds work in any browser. The classroom notes assume fifty minutes, students who are trying, and chalk. Everything is free. No signup, no paywall, no email gate.
What’s queued
Four more models are flagged in the catalog as next: AD-AS, Mundell-Fleming, Ricardian comparative advantage, and Cournot duopoly. After that — externalities and Pigouvian taxation, search-and-matching for unemployment, endogenous growth, behavioural departures. The list of canonical models worth teaching is long. For now, eight.
If you’re teaching from any of them this semester, or learning from any of them on your own — and the explanation in the classroom-notes section doesn’t quite land — write to info@leadafrik.com and tell me where it broke. That’s the feedback that improves the next version.
Find them at /models. Pick the one closest to whatever’s confusing you right now. Move the sliders. See if the third try does the trick.
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