Skip to content

IS–LM model

A two-curve diagram fixing short-run equilibrium in a closed economy: the downward IS curve where the goods market clears and the upward LM curve where the money market clears cross at one point (r, Y) that pins down the interest rate and output jointly.

Core Idea

The IS–LM model, introduced by Hicks (1937) to formalize Keynes, is a two-curve graphical apparatus for short-run equilibrium in a closed economy with a goods market and a money market. The IS curve traces all combinations of interest rate and output where the goods market clears (sloping down); the LM curve traces where the money market clears (sloping up). Their intersection yields the unique equilibrium (r, Y) at which both markets clear simultaneously — the model's central result.

Scope of Application

The IS–LM model lives within macroeconomics — the subfields and uses sharing its goods-and-money closed-economy substrate, bounded by that monetary-economy frame.

  • Undergraduate and intermediate macro teaching — the canonical first formal model.
  • Short-run policy comparative-statics — "what happens to output if spending rises by X?"
  • Open-economy macroeconomics — the Mundell–Fleming extension yielding the impossible trinity.
  • History of macroeconomic thought — the bridge between Keynes and the neoclassical synthesis.
  • Central-bank public communication — still used to explain policy where DSGE runs internally.

Clarity

The model first makes visible that the goods and money markets clear jointly, not sequentially — output and the interest rate are determined together at one intersection. This dissolves the classical and naive-monetarist positions as special cases of one picture. Its sharper service converts the open-ended fiscal-versus-monetary debate into a determinate question about the slope of the LM curve, a structural parameter with observable content.

Manages Complexity

IS–LM compresses an unmanageable multi-market economy to two clearing loci on one (r, Y) plane and a single tracked object: the intersection. Two further compressions make it a working tool — any shock reduces to which curve it shifts and in which direction (four canonical movements), and the fiscal-versus-monetary debate contracts to one slope parameter, the interest elasticity of money demand, at the cost of everything the two curves suppress.

Abstract Reasoning

The model's primary move is shock-to-curve-shift decomposition, resting on a joint-determination move that corrects the "output or interest rate?" error. Its sharpest move is regime identification by curve slope, turning an ideological dispute into a parameter reading. A compositional-extension move builds Mundell–Fleming by adding a curve, and an explicit boundary condition disciplines its jurisdiction as a first-pass diagnostic.

Knowledge Transfer

Within macroeconomics IS–LM transfers as mechanism across the subfields sharing its closed-economy substrate — teaching, policy comparative-statics, the Mundell–Fleming extension, the history of thought, central-bank communication — carrying its limitations as a package. Beyond macroeconomics the model itself does not travel: its curves and parameters have no referent outside a goods-and-money economy. The substrate-independent insight beneath it — coupled markets clear jointly at the crossing of their clearing conditions — is carried by the parent prime general_equilibrium, not by IS–LM.

Relationships to Other Abstractions

Local relationship map for IS–LM modelParents appear above the current abstraction, mutual partners to the right, and children below. Node labels state whether each abstraction is prime or domain-specific; colors identify relation types.IS–LM modelDOMAINPrime abstraction: Comparative Statics — is part ofComparativeStaticsPRIMEPrime abstraction: Equilibrium — presupposesEquilibriumPRIMEDomain-specific abstraction: Aggregate Demand — presupposes, typicalAggregate DemandDOMAIN

Current abstraction IS–LM model Domain-specific

Parents (2) — more general patterns this builds on

  • IS–LM model is part of Comparative Statics Prime

    IS–LM contains comparative statics as the curve-shift and old-versus-new intersection operation that produces its policy results.

  • IS–LM model presupposes Equilibrium Prime

    IS–LM presupposes equilibrium because its defining point simultaneously clears the coupled goods and money markets.

Children (1) — more specific cases that build on this

  • Aggregate Demand Domain-specific presupposes, typical IS–LM model

    Aggregate demand typically presupposes IS–LM when the schedule is derived by tracing joint goods-money equilibrium output across price levels.

Hierarchy paths (2) — routes to 1 parentless root

Neighborhood in Abstraction Space

IS–LM model sits in a crowded region of the domain-specific corpus (24th percentile for distinctiveness): several abstractions share nearly its structure, so a description that fits it tends to fit its neighbors too.

Family — Macroeconomic Equilibria & Consumer Demand (19 abstractions)

Nearest neighbors

Computed from structural-signature embeddings · 2026-07-12