S = I

Definition

The national saving and investment identity, also known as the saving-investment identity, is an accounting identity that states that national saving (S) is equal to national investment (I) in a closed economy. This identity is a fundamental concept in macroeconomics that helps understand the relationship between saving and investment in an economy.

5 Must Know Facts For Your Next Test

1. The saving-investment identity, S = I, holds true in a closed economy where there is no foreign sector involved.
2. In a closed economy, national saving must be equal to national investment because any saving not used for domestic investment will not be used at all.
3. The saving-investment identity is an accounting identity, meaning it is true by definition and does not depend on any behavioral assumptions or economic theory.
4. The saving-investment identity is a useful tool for understanding the macroeconomic relationships between saving, investment, and other economic variables, such as consumption and government spending.
5. The saving-investment identity is a fundamental concept in the study of the business cycle, as changes in saving and investment can affect the level of economic activity and employment.

Review Questions

• Explain the relationship between national saving (S) and national investment (I) in the context of the saving-investment identity.
  • The saving-investment identity, S = I, states that in a closed economy, the total amount of national saving (S) must be equal to the total amount of national investment (I). This means that all the income that is not consumed (saved) is used to finance investment in capital goods, such as machinery, equipment, and structures. The identity reflects the fact that in a closed economy, any saving not used for domestic investment will not be used at all, as there is no foreign sector to lend or borrow from.
• Describe the role of the saving-investment identity in understanding the macroeconomic relationships between economic variables.
  • The saving-investment identity is a useful tool for understanding the macroeconomic relationships between saving, investment, and other economic variables, such as consumption and government spending. It helps explain how changes in one variable, such as an increase in saving, can affect other variables, such as investment and economic growth. For example, an increase in saving may lead to a corresponding increase in investment, as the additional saving provides the funds necessary for businesses to invest in capital goods. Understanding these relationships is crucial for policymakers and economists in analyzing and predicting the effects of economic policies on the overall economy.
• Analyze the importance of the saving-investment identity in the study of the business cycle and its impact on economic activity and employment.
  • The saving-investment identity is a fundamental concept in the study of the business cycle, as changes in saving and investment can affect the level of economic activity and employment. During periods of economic expansion, for instance, increased investment in capital goods can lead to higher levels of production and employment. Conversely, a decline in investment during economic downturns can result in lower levels of economic activity and higher unemployment. The saving-investment identity helps economists and policymakers understand these dynamics and formulate appropriate policies to stabilize the economy and promote sustainable economic growth. By analyzing the relationship between saving and investment, economists can better predict and respond to fluctuations in the business cycle, which is crucial for maintaining full employment and stable economic conditions.

Related terms

National Saving (S): The total amount of income in an economy that is not consumed, representing the portion of income that is set aside for future use, such as investment or net foreign lending.

National Investment (I): The total spending on capital goods, such as machinery, equipment, and structures, as well as changes in business inventories, which are used to produce future goods and services.

Closed Economy:

An economy that does not engage in any trade (import or export) with other economies, where all the goods and services produced are consumed domestically.