Every person who earns money faces a simple choice spend or save. Economists study this behavior to understand how changes in income affect saving and spending patterns. One of the key concepts in this area is the marginal propensity to save, often abbreviated as MPS. It measures how much of an additional unit of income a person chooses to save rather than spend. By analyzing examples of marginal propensity to save, we can better understand personal finance decisions and the broader functioning of an economy.
What Is Marginal Propensity to Save?
The marginal propensity to save (MPS) refers to the proportion of any additional income that an individual decides to save instead of spending on consumption. It plays a central role in macroeconomics, particularly in the Keynesian model, which explores how income and spending drive economic growth. MPS is closely related to another concept known as the marginal propensity to consume (MPC), which measures how much of an extra dollar of income is spent.
The Basic Formula
The formula for marginal propensity to save is simple
MPS = Change in Savings ÷ Change in Income
This equation shows that MPS depends on how much additional income is saved when income changes. For example, if your income increases by $100 and you save $20 of that, your MPS would be 0.2.
Relationship Between MPS and MPC
Marginal propensity to save (MPS) and marginal propensity to consume (MPC) always add up to 1. This is because every extra unit of income must either be spent or saved. If a person spends 80% of their additional income, they must save 20%, and vice versa. Mathematically, it can be expressed as
MPS + MPC = 1
This relationship helps economists understand how income distribution affects the total demand and savings within an economy.
Simple Example of Marginal Propensity to Save
Imagine a worker named Sarah who earns $2,000 per month. One day, she receives a raise that increases her monthly income by $500. Out of that $500, she decides to save $100 and spend the remaining $400 on groceries, entertainment, and clothes. In this case
- Change in income = $500
- Change in savings = $100
- MPS = $100 ÷ $500 = 0.2
This means Sarah saves 20% of her extra income and spends the rest. Her marginal propensity to consume (MPC) would therefore be 0.8 (since 1 – 0.2 = 0.8). This simple example shows how MPS reflects the tendency of individuals to save from any increase in income.
Understanding MPS Through Real-Life Scenarios
Marginal propensity to save can vary depending on a person’s financial situation, lifestyle, and the economy’s overall condition. Here are several examples and cases that demonstrate how MPS works in different contexts.
1. Example of Low-Income Households
People with low incomes tend to have a low MPS because they need to spend most of their additional income on necessities such as food, rent, and utilities. For instance, if a worker earning $1,000 a month receives an extra $200 and uses $190 for essentials, they save only $10. Their MPS would be $10 ÷ $200 = 0.05. This shows that when income is limited, saving is often less of a priority than meeting basic needs.
2. Example of High-Income Individuals
High-income earners, on the other hand, usually have a higher marginal propensity to save. Because their essential needs are already met, they are more likely to save a portion of any additional income. Suppose a business executive earns $10,000 a month and gets a $2,000 bonus. If they save $800 of that, their MPS is $800 ÷ $2,000 = 0.4. This indicates a stronger inclination to save, which is common among wealthier individuals.
3. Economic Downturn Scenario
During an economic recession, people often increase their MPS because they fear losing jobs or income stability. For example, if someone’s income increases by $1,000 during uncertain times and they save $600 to prepare for potential risks, their MPS becomes 0.6. Higher saving rates during downturns can slow economic recovery, as less spending leads to lower demand for goods and services.
4. Booming Economy Example
In contrast, during periods of economic growth and confidence, individuals may have a lower MPS because they feel secure about the future. For instance, if someone earns an extra $500 and saves only $50 while spending $450, their MPS is $50 ÷ $500 = 0.1. In such times, people are more comfortable consuming, which stimulates economic activity.
Factors Influencing Marginal Propensity to Save
Many factors determine how much of an additional income a person decides to save. These factors include income level, cultural attitudes toward saving, government policies, and personal financial goals.
1. Income Level
As mentioned earlier, people with higher incomes generally have a greater ability to save, while those with lower incomes spend more of their earnings. This difference affects national saving rates and economic stability.
2. Interest Rates
When interest rates are high, saving becomes more attractive because individuals earn more from deposits. As a result, MPS tends to rise. Conversely, when interest rates are low, people may prefer to spend rather than save.
3. Cultural and Social Factors
In some cultures, saving is seen as a moral or practical virtue, leading to a higher MPS. In others, consumption and enjoyment of income are valued more, resulting in lower saving rates. Social expectations and financial education also play a major role.
4. Economic Policies and Taxes
Government policies can directly influence MPS. For example, tax incentives for savings accounts or retirement plans encourage people to save more. On the other hand, high taxes may reduce disposable income, lowering the ability to save.
5. Future Expectations
People’s confidence about the future also impacts saving behavior. When individuals expect stable jobs and rising incomes, they tend to spend more and save less. However, uncertainty about future income increases the marginal propensity to save as a form of financial security.
Macroeconomic Importance of MPS
The concept of marginal propensity to save is essential in understanding how income changes affect an entire economy. It helps economists predict how policies like tax cuts, stimulus payments, or wage increases will influence overall savings and spending behavior.
Impact on the Multiplier Effect
MPS plays a central role in calculating the multiplier effect in economics. The multiplier shows how an initial change in spending leads to a larger overall impact on national income. The formula for the multiplier is
Multiplier = 1 ÷ (1 – MPC) or 1 ÷ MPS
This means that when MPS is low (and MPC is high), the multiplier is larger, leading to a greater economic impact. Conversely, a higher MPS reduces the multiplier, as more income is saved instead of spent.
Influence on Economic Growth
While high savings can support investment and long-term growth, excessive saving in the short term may slow down economic activity. Economies with balanced MPS values tend to maintain steady growth, as there is enough saving for investment and enough spending to sustain demand.
Practical Example for Better Understanding
Let’s consider an example involving a community of workers. Suppose a company increases wages for all its employees, leading to an average income rise of $1,000 per person. Surveys show that, on average, each employee saves $300 of the additional income and spends $700.
- Change in income = $1,000
- Change in savings = $300
- MPS = $300 ÷ $1,000 = 0.3
This means that 30% of the new income is saved and 70% is spent. From an economic perspective, this balance supports both personal financial security and the local economy, as savings contribute to future investments while spending fuels immediate economic activity.
The marginal propensity to save provides deep insight into how individuals and economies manage additional income. Whether it’s a small raise or a national income shift, MPS helps explain how much of that increase will be set aside for the future. Through examples such as Sarah’s raise, low-income families, or high-income savers, it becomes clear that saving habits vary widely but follow predictable patterns. Understanding these patterns allows policymakers, businesses, and individuals to make smarter decisions that balance growth and financial stability. In essence, MPS reflects one of the most fundamental aspects of economics—the delicate relationship between earning, spending, and saving that shapes the rhythm of every economy.