Cognitive Scaffold

Preparing your thinking workspace

arrow_back_ios_new
MENTAL MODEL · M3927

Fisher Equation

Fisher Equation
BusinessHigh supportMacroeconomics
Included
account_tree

Updated 2026-08-01

Loading revision record…

INTRODUCTION

English translation pending.

CORE DEFINITION

Formulated by Irving Fisher in The Purchasing Power of Money, the equation of exchange is written MV = PT, where M is the money supply, V its velocity of circulation, P the price level and T the volume of transactions, often replaced by real output Y. It is the central identity of the quantity theory of money and the foundation of monetarism. As an accounting identity it holds by construction; its predictive force comes from the added assumption that V and T are stable in the short run, so movements in M pass through to P.

SCAFFOLDING EFFECT

psychology

Reduce cognitive load

- Inflation triage: identify whether M, V or T is the driver before blaming prices. - Velocity check: test whether V is stable before trusting money-growth forecasts. - Policy design: choose between money-supply rules and interest-rate rules by watching velocity.

anchor

Anchor fast decisions

Money is a medium of exchange, so total spending equals the quantity of money multiplied by the number of times each unit is spent. Total spending is also the price level multiplied by the quantity of goods traded. Because both expressions describe the same flow, an increase in M that is not offset by a fall in V or a rise in T must show up as a higher P. Inflation therefore becomes a monetary phenomenon whenever the non-monetary terms are stable.

MINIMUM ACTION

In progress 0/1

Practice this model in one real situation:

Check to track your progress (stored locally)
Learning progress0%
account_treeGenealogyexpand_more
menu_bookReferencesexpand_more

Source support: Explicit

  • link
    zh.wikipedia.orghttps://zh.wikipedia.org/wiki/%E8%B2%BB%E9%9B%AA%E6%96%B9%E7%A8%8B%E5%BC%8FZH · Explicit
    verified

RELATED MODELS

Related model

Total Factor Productivity - TFP

In macroeconomics, total factor productivity (TFP), also known as total factor productivity or rate of technological progress, refers to all factors affecting output other than external inputs such as capital and labor. In simple terms, it is the improvement in the intrinsic strength of an economy, characterized by its ability to explain the factors of economic growth through a single simple figure.

arrow_forwardRelated model

Kondratiev Waves

In modern capitalist economies, the Kondratiev wave theory, also known as 'long waves', 'K-waves', or 'Kondratiev long waves', describes an economic cycle phenomenon with a period of approximately 50-60 years. The long wave is generally divided into two phases: the upward A-phase and the downward B-phase. This phenomenon can be explained by the technology life cycle. The name 'long wave' originates from the Soviet economist Nikolai Kondratiev, who proposed this view in his work 'The Major Economic Cycles' (1925) and other writings of the same period. Earlier, two Dutch economists, J. van Gelderen and Samuel de Wolff, had already deduced similar phenomena in 1913. Kondratiev's long wave theory first appeared in the book 'The World Economy and Its Fluctuations During and After the War' (completed in 1919-1920, published in 1922). Subsequently, he further developed the theory of long waves...

arrow_forwardRelated model

Liquidity Trap

A liquidity trap is a situation, described in Keynesian economics, in which, "after the rate of interest has fallen to a certain level, liquidity preference may become virtually absolute in the sense that almost everyone prefers holding cash rather than holding a debt (financial instrument) which yi…

arrow_forward