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Money and the Multiplier Effect: How Reserve Ratios Work and Why They Matter
Business Essentials · Chapter 23: Money and the Federal ReserveSection 23.2 · lesson 98 of 10511 min · free with a free account
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In this lesson
How reserve ratios work, and why they matter.
- Explain how banks create money by lending
- Calculate the deposit multiplier
- Name the 3 factors that shrink the real expansion
- Distinguish reserve requirements from capital requirements
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Money and the Federal Reserve
Money and the Multiplier Effect
Here's a question most people never ask. Where does money in a bank account actually come from? The answer is stranger, and more important, than it first sounds. This is educational content about deposit creation and reserve requirements. It isn't financial, investment, tax, or legal advice. Reserve requirements have been changed by policymakers over time, including being set to zero at points. So any ratio in this section is illustrative only. Current requirements should always be verified. We'll see how banks create money through lending, and calculate the deposit multiplier. We'll look at the three factors that keep real expansion below the theoretical maximum. And we'll separate reserve requirements from capital requirements, which are easily confused.
The Question
Where Do Deposits Come From?
The last section established that most money is bank deposits, not physical currency. That raises an immediate question. Where do those deposits come from? The answer is that banks create them, when they lend. That isn't a figure of speech, or a loose metaphor. It describes the literal mechanics of how a bank records a loan. And it's essential to understanding how the money supply expands, and how it contracts. Once you see it, a lot of headlines about banks and credit start to make more sense. So let's walk through exactly how it works.
Fractional Reserves
Lending Creates a New Deposit
Modern banking runs on a system called fractional reserve banking. A bank holds only a fraction of its deposits as reserves. It lends the remainder to borrowers. Reserves are funds kept on hand, or at the central bank, rather than lent out. Now here's the part most people get wrong. When a bank makes a loan, it doesn't usually hand the borrower physical cash. And it isn't passing along some other depositor's funds. Instead, it credits the borrower's own deposit account with the loan amount. That creates a new deposit, one that didn't exist before the loan was made. So the act of lending is itself the act of creating a new deposit. That's the central mechanism of this whole section.
Worked Through
Deposit Creation, Round by Round
Let's work it through, with an illustrative reserve ratio of ten percent. That ratio is constructed for this exercise. It isn't any current requirement. Ten percent means the bank must hold ten percent of each deposit as reserves, and may lend the other ninety. A customer deposits one thousand dollars. The bank holds one hundred dollars as reserves, and lends nine hundred to a borrower. The borrower spends that nine hundred dollars. Whoever receives the payment deposits it in a bank. That bank holds ten percent, or ninety dollars, as reserves, and lends out eight hundred ten. And the process continues. Each round's new deposit is ninety percent of the round before it. The reserves held keep adding up, and the amount available to lend shrinks round by round.
Worked Rounds
5 Rounds From a 1,000 Deposit
Here are the first five rounds, using those same illustrative figures. Round one, the original one thousand dollar deposit. One hundred is held, and nine hundred lent onward. Round two, a new deposit of nine hundred dollars. Ninety held, eight hundred ten lent. Round three, eight hundred ten dollars deposited, and seven hundred twenty-nine lent. By round five, the new deposit has shrunk to about six hundred fifty-six dollars. Now watch the last column, the cumulative total of deposits. After just five rounds, it has passed four thousand ninety-five dollars. And as the rounds continue, it keeps climbing toward a theoretical maximum of ten thousand dollars. So one original deposit, lent and redeposited again and again, supports deposits several times its own size. That's deposit creation in concrete, worked form.
The Multiplier
The Deposit Multiplier
That theoretical maximum has a name. It's the deposit multiplier. It's the largest expansion of deposits that an initial deposit can support. You calculate it as the reciprocal of the reserve ratio. That is, one divided by the reserve ratio, expressed as a decimal. With our illustrative ratio of ten percent, that's one divided by zero point one zero. The answer is ten. So the theoretical maximum is ten times the original deposit. Ten thousand dollars, from one thousand. The relationship holds generally. A lower reserve ratio produces a larger multiplier, because banks can lend more of each deposit. A higher reserve ratio produces a smaller one, because banks must hold more back.
Table 23.2.1
Why the Real Expansion Is Smaller
In practice, that theoretical maximum rarely happens. Three factors pull real expansion below it. The first is currency held outside banks. Cash a person keeps, rather than redepositing, can't support another round of lending. Every dollar that leaves the banking system that way stops the multiplication. The second is excess reserves, reserves banks choose to hold beyond what's required. A bank doing that is lending less than the maximum, out of caution, weak loan demand, or other business reasons. The third is the most fundamental. There have to be willing, creditworthy borrowers. A bank can't create a deposit through lending if no qualified borrower seeks, or receives, a loan. Each factor works independently, and each can push the real multiplier well below its theoretical value. And in a downturn, it's the third factor that binds most tightly.
The Binding Constraint
Reserves Are Necessary, Not Sufficient
That third factor explains a pattern that can seem puzzling. Banks may hold ample reserves. They may be fully willing to lend. And yet lending, and the deposit expansion it would create, doesn't increase. Why not? Because businesses and households, worried about the outlook, aren't seeking new loans. And in weaker conditions, banks judge fewer applicants to be creditworthy. So reserves are a necessary condition for lending. But they aren't a sufficient one. That's precisely why increasing bank reserves doesn't automatically increase lending. Anyone who assumes ample reserves mean easy credit is overlooking these three factors. Especially the third.
Reserve Requirements
A Regulatory Tool That Has Changed
A reserve requirement is a regulation. It sets the minimum fraction of deposits a bank must hold as reserves. It works as a tool, influencing how much banks can lend, and so how far the money supply can expand. Here's the essential accuracy point. The reserve requirement framework has changed over time. At points, requirement ratios have been set to zero, for some or all categories of deposit. So any specific ratio must be verified with an authoritative source, never assumed to still apply. What stays constant is the mechanism. Whatever fraction is required, if any, it works by constraining how much of each deposit a bank may lend. And the multiplier logic applies to whatever ratio is actually in effect. Central banks have also shifted which tools they mainly rely on. They've moved from an emphasis on reserve requirements toward tools like interest paid on reserves, and other administered rates. We'll cover the present framework when we reach the Federal Reserve's tools.
Not The Same Thing
Reserves Versus Capital
Reserve requirements and capital requirements are frequently confused. The distinction matters. Reserves concern liquidity. Does the bank have enough readily available funds to meet withdrawals, and settle payments day to day? Capital concerns solvency. Are the bank's own resources, contributed by owners and retained from earnings, enough to absorb losses on its loans and assets? If not, it may be unable to meet its obligations to depositors and other creditors. Here's why the difference matters. Either problem can exist without the other. A bank can be short of reserves on a given day, and still be entirely solvent. That liquidity problem is often solved with short-term borrowing. And a bank can hold ample reserves while being critically undercapitalized. That's a solvency problem, and liquidity alone can't fix it.
So What
Implications, and the Model's Limits
What does this mean for a business? The central implication is that credit availability moves with bank willingness to lend, not just with policy. A business seeking a loan is affected by the broad monetary environment, and by where we are in the business cycle. But it's also affected by the lending posture of the specific banks it approaches. That posture reflects how much in excess reserves those banks choose to hold. And how creditworthy they judge the pool of applicants, including the business itself, at that point in the cycle. So a business's own financial position interacts with banking conditions, in deciding what credit it can actually get. One honest caveat about everything in this section. The simple multiplier model is a teaching device. It's a simplification of how modern banking works. Real banks manage lending, reserves, and capital at the same time, against many requirements and their own risk practices. The model's value is in making deposit creation visible. It doesn't predict the expansion that will actually occur.
Case Vignette
Reserves Without Loans
Ingrid owns a mid-sized construction firm. This is a composite case, constructed for instruction. She wants a loan for new equipment. The news says the banking system is holding unusually large reserves. So she expects credit to be readily available. Instead, her application meets caution, and is finally declined. Her loan officer explains, without discussing any other applicant, that the bank has become more conservative in this downturn. It's holding more than the required reserves. Not because it can't lend, but because it judges fewer applicants creditworthy. And demand for borrowing from qualified applicants has fallen, as businesses grow more cautious. Ingrid's need for the equipment is genuine. But the lending environment is shaped by conditions well beyond her control. No amount of explaining her firm's soundness fully overcomes a system-wide shift toward caution. With her financial adviser, she reaches a clear conclusion. Ample reserves don't translate mechanically into available credit. In a downturn, the binding constraint is willing lending and confident, qualified borrowing, not the quantity of reserves. So she'll plan her firm's financing timeline with that reality in mind.
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About Money and the Multiplier Effect: How Reserve Ratios Work and Why They Matter
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What is the difference between reserve requirements and capital requirements?
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