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The marginal propensity to save (MPS) refers to the amount of disposable income a consumer is able to save. It’s used to reflect the proportion someone is willing to save for each additional dollar of their income.

To understand why MPS is important when quantifying fluctuations in savings and income, we’ll go over how to calculate MPS and how to apply it to your budgeting strategy.

What is the Marginal Propensity to Save?

The marginal propensity to save is defined as the portion of an increase in income that goes towards household savings. In other words, it’s the percentage of additional income a household saves instead of spending on goods and services, and it offers insight into the consumption habits of consumers.

MPS is also referred to as leakage, where the savings is an amount (expressed as a percentage that doesn’t go back into the economy via consumption. Typically, the more a household saves, the more likely it indicates that there is a higher income and better equipped to cover their household expenses.

So, theoretically, if a household saves 10%, it means that for every additional dollar they earn, they’ll save 10 cents.

When consumers are more likely to save as their income grows, the chances are higher they’ll become wealthier. Plus, households will also be able to access services and goods that require more money, such as larger homes in higher cost of living areas, elaborate vacations, or luxury vehicles.

How Income Level Affects Marginal Propensity to Save

Given data on household income and household saving, economists can calculate households’ MPS by income level. This calculation is important because MPS is not constant—it varies by income level. Typically, the higher the income, the higher the MPS because as wealth increases so does the ability to satisfy needs and wants, and so each additional dollar is less likely to go toward additional spending. However, the possibility remains that a consumer might alter savings and consumption habits with an increase in pay.

The Multiplier Effect

The MPS plays an important part in regulating the multiplier effect. The multiplier effect looks at the proportional increase or decrease in income that comes from consumption or savings.

For instance, if there is spending at the government level, it’ll have a multiplier effect (much like how a snowball rolls down a hill) on different parts of the economy. This change is due to the fact there is now additional disposable income consumers can spend on consumption and savings.

By understanding what the MPS is, economists can see how increased government spending can influence savings. It’ll also help to determine how consumers’ saving habits will influence the overall economy. The lower the MPS, the more of an impact on changes in government spending there will be.

Calculating the Marginal Propensity to Save

Calculating the MPS involves dividing the change in savings by a change in disposable income.

The following formula is used to calculate the MPS:

MPS = change in savings / change in disposable income

The savings represented by the value of the MPS will change if income changes by a dollar. Presented on a graph, the MPS is the equivalent of the savings line that’s created by plotting changes in income on the horizontal line (x-axis) and changes in savings on the vertical line (y-axis).

Another important point to note is that MPS will range between zero and one. If the MPS is zero, then it means changes in income doesn’t have an effect on savings (consumers spend all additional income). If MPS is one, then all additional income is saved.

Example

Jasmine successfully negotiated a promotion and annual bonus and received an additional $3,000 with her next paycheck. Jasmine decides she wants to spend this amount on a nice dinner out with friends totaling $150, and a vacation in Mexico for $2,000. The total she spends out of her bonus is $2,150, saving $850.

Using the above MPS formula, the calculation is as follows:

$850 / $3,000 = 0.283 = 28.3%

Therefore, Jasmine saved 28% of her additional income or 28 cents for each additional dollar she earns.

Remember, MPS isn’t constant since various factors in addition to changes in income will influence consumer spending habits. For instance, the time of the year can influence seasonal trends, which can correlate with higher spending.

Applying MPS to Your Budget Strategy

Though it seems like MPS is more for economists, you can apply this tactic to your personal budget.

When it comes to increasing your income, it might be tempting to spend a large portion of it. After all, you might want to celebrate a pay raise or promotion. Or, you might decide to increase your grocery budget, swapping out some of your regular produce for organic varieties.

However, there are benefits to saving some of the extra money. Perhaps you have a financial goal you can use it towards, like saving for a down payment on a house. Or you want to start investing and with this boost in income, you now have the means to do so.

If you haven’t yet decided what you’re saving for, just getting into the habit of saving will get you on the right track. Plus, you’ll learn how to budget effectively, no matter which type of budgeting technique you use.

Let’s say you want to be able to set aside 20% of each paycheck towards investments and a larger emergency fund. You received a $1,000 bonus from work this month and want to make sure you’re not tempted to spend it all.

Using the above formula, you want to have an MPS of 30%, or 0.3. That means with that bonus, you want to be able to save $300, allowing you to put $800 of it towards other areas in your budget. Once you have this number, you can take proactive steps to save that money. Automatically transferring $300 to a separate savings account is a good start.

Considering your income may fluctuate, you’ll probably want to revisit this formula on occasion to make sure you’re on track. Plus, it’s likely your spending habits will also change—such as spending more during the holidays—so if you need to spend more, then you can adjust your savings rate temporarily. At the end of the day, it’s all about being aware of where your money is going.

Recommended: 39 Ways to Earn Passive Income Streams

The Takeaway

Marginal propensity to save may seem like a term that doesn’t relate to your budget since it’s normally used to help economists. However, thinking about it in simple terms such as a savings rate is more helpful. That way, you can use it to apply it towards your savings goals and budgeting tactics as your income changes.

Saving money is half the battle: making sure your money is working for you is the other half. Opening a checking and savings account with SoFi can earn you more than the national interest average, squeezing even more value from your hard-earned dollars.

Photo credit: iStock/Toxitz

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