The Keynesian Doctrine and its Impact on Economic Policies

André Gonçalves de Freitas

Hatched by André Gonçalves de Freitas

Apr 19, 2024

3 min read


The Keynesian Doctrine and its Impact on Economic Policies


The Keynesian doctrine, named after the renowned British economist John Maynard Keynes, revolutionized the way governments interact with the economy. This doctrine introduced the idea that the public budget could be used as a tool for fiscal policy, a concept that contrasted with prevailing economic concepts at the time. Keynes argued that during economic recessions, the government could intervene and stimulate the economy through increased public spending. This intervention could take various forms, such as direct investment in infrastructure or tax reductions to encourage private consumption and investment.

The Keynesian Approach to Fiscal Policy:

Keynesian economics advocates for an expansionary fiscal policy during times of economic downturns. By increasing government spending, aggregate demand can be boosted, leading to increased production and employment. Conversely, during economic expansions, the government can use the public budget as a tool to prevent overheating of the economy by reducing public spending or increasing taxes to reduce aggregate demand.

The Keynesian Model:

The Keynesian model incorporates consumption, investment, government, and the external sector to determine equilibrium income. In this model, the aggregate supply curve is horizontal, with prices and wages being rigid. The multiplier effect, which measures the increase in income resulting from an increase in spending, becomes larger when certain conditions are met.

Calculating Equilibrium Income:

Considering a simple Keynesian model with consumption given by the function C = 100 + 0.2Y, where C represents consumption and Y represents income, let's determine the equilibrium income and the tax rate applied to income. Assuming an autonomous investment and autonomous government spending equal to 10 each, and a marginal propensity to consume of 40%, we can calculate the equilibrium income and tax rate.

The Role of Import Propensity:

In the Keynesian model with consumption, investment, government, and the external sector, an increase in the marginal propensity to import and a reduction in the marginal propensity to consume affect equilibrium income. By analyzing these factors, we can gain insights into the potential impact on the economy.

The New Keynesian Theory:

The New Keynesian theory introduces the concept of menu costs, which explains the stickiness of prices in the short run. According to this theory, firms incur costs when adjusting prices, leading to price rigidity and slower adjustment to changes in demand. Understanding these costs can help policymakers design effective economic policies.


The Keynesian doctrine has had a profound impact on economic policies worldwide. By advocating for government intervention through fiscal policies, Keynesian economics aims to stabilize the economy and prevent severe fluctuations. Three actionable pieces of advice derived from Keynesian principles are:

  • 1. During economic downturns, consider implementing expansionary fiscal policies, such as increasing public spending, to stimulate aggregate demand and boost production and employment.
  • 2. During economic expansions, use contractionary fiscal policies, such as reducing public spending or increasing taxes, to prevent overheating of the economy and control inflation.
  • 3. Incorporate the analysis of import propensity and consumption patterns into economic models to gain a comprehensive understanding of their impact on equilibrium income.

By applying these principles and incorporating Keynesian insights into economic policymaking, governments can strive for stability and growth in their economies.

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