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La IS LM, el modelo macroeconómico más influyente
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La IS LM, el modelo macroeconómico más influyente

The IS-LM Model: A Key Framework in Macroeconomics

Overview of the IS-LM Model

  • The IS-LM model, developed by John Hicks, is recognized as one of the most successful frameworks in macroeconomics, gaining significant acceptance among economists throughout the 20th century and continuing to influence policy analysis today.

General Theory vs. Specific Theories

  • Hicks critiques the "General Theory," suggesting it does not encompass all economic theories; he aims to create a general theory that includes classical economics and Keynesian perspectives as specific cases.

Market Equilibrium Concepts

  • The model focuses on three markets: money, goods, and bonds. Hicks posits that establishing equilibrium in two out of these three markets suffices to ensure equilibrium in the third market due to the law of redundancy.

Determining Economic Equilibrium

  • In this framework, income level (Y) and interest rate (i) are key variables. The intersection of the IS curve (goods market equilibrium) and LM curve (money market equilibrium) determines overall economic equilibrium.

Understanding Demand for Goods

  • The IS curve represents combinations of income levels and interest rates where goods market demand equals supply. Demand can be broken down into consumption, investment, and government spending—where government spending is exogenous.

Relationship Between Interest Rates and Income Levels

  • A negative relationship exists between interest rates and income levels; higher interest rates lead to lower consumption/investment, resulting in lower income levels at equilibrium.

Special Case: Keynesian Perspective

  • In a Keynesian scenario within this model, consumption depends solely on income while investment remains insensitive to interest rates. This results in a vertical IS curve under extreme conditions.

Fiscal Policy Implications

Effects of Fiscal Policy on IS Curve

  • Expansionary fiscal policy shifts the IS curve rightward while contractionary policy shifts it leftward. These movements illustrate how fiscal measures impact overall economic activity through changes in demand for goods.

Money Market Dynamics

Understanding Money Supply and Demand

  • In the money market context, equilibrium occurs when money supply equals money demand. Real balances are calculated by dividing nominal money supply by price level.

Components Influencing Money Demand

  • According to Keynesian theory, money demand arises from transaction motives (linked with income), precautionary motives (also linked with income), and speculative motives (inversely related to interest rates).

Speculative Motives for Holding Money

Conventional Interest Rate Expectations

  • Individuals form expectations about future interest rates based on current levels; if current rates are low, they anticipate increases which influences their decision to hold or lend money accordingly.

Understanding Money Demand and Interest Rates

The Relationship Between Income Levels and Money Demand

  • The demand for money is influenced by income levels and speculative motives, with the total demand equating to the real money supply. A lower income level results in decreased transaction and precautionary demands for money.
  • To achieve equilibrium in the money market with low income, a high speculative demand for money is necessary, which can be facilitated by low interest rates.
  • Conversely, high income levels lead to increased transaction and precautionary demands for money; thus, a higher interest rate would reduce speculative demand.

Classical vs. Keynesian Perspectives on Money Demand

  • In classical economics, speculation does not affect money demand; it solely depends on income levels, resulting in a vertical LM curve.
  • In contrast, Keynesian economics emphasizes speculation as the primary factor affecting money demand, leading to a horizontal LM curve.

Effects of Monetary Policy on the LM Curve

  • Changes in monetary policy directly impact the LM curve: an expansionary monetary policy shifts it rightward while a contractionary policy shifts it leftward.
  • The intersection point of IS and LM curves determines economic outcomes; if they intersect at the horizontal part of the LM curve (Keynesian case), fiscal policies can effectively increase income without significantly affecting interest rates.

Effectiveness of Fiscal vs. Monetary Policies

  • In a Keynesian framework, expansionary monetary policy may be ineffective if intersection points remain unchanged; however, fiscal policies are effective in increasing income levels.
  • In classical economics, expansionary fiscal policies have limited effects due to verticality of the LM curve—resulting in minimal changes to income levels despite shifts in aggregate supply.

Synthesis of Economic Theories

  • The discussion between Keynesians (fiscalists) and classical economists (monetarists) highlights differing views on effective economic policies within an IS-LM model framework.
  • While IS-LM provides clarity on theoretical discussions regarding macroeconomic policies throughout the 20th century, its simplicity has led to misconceptions about economic policymaking's complexity.
Video description

Durante el último siglo, el modelo de la síntesis neoclásica fue el más usado en macroeconomía y todavía tiene influencia a la hora de analizar las políticas económicas monetaria y fiscal. Aquí se explica el modelo IS LM de John Hicks y las diferencias entre keynesianos y monetaristas. Errata: en el momento 3:10 la tasa de interés es alta. El video se basa en el artículo Mr Keynes y los clásicos. Hicks, J R (1937) Mr Keynes and the "classics" a suggested interpretation. Econometrica.