Difficulty: Intermediate | Prerequisites: Chapter 10 (money supply, banking system, the Fed's tools).
Big picture: This is the demand side of the money market. Earlier chapters covered how the banking system creates money (the supply side). Now you need to understand why people choose to hold money rather than bonds, how the interest rate drives that decision, and how changes in income or prices shift the entire demand curve. Getting this right is essential before you can analyse how the Fed's actions move the equilibrium interest rate in Part 2.
Source: Principles of Macroeconomics, Case/Fair, 8e – Chapter 11, Section 11.1
Tags: money demand, demand for money, opportunity cost of holding money, nonsynchronization, optimal money balance, transaction motive, speculative motive, bond prices, interest rate, macroeconomics
People hold money for transactions and for speculation. The interest rate is the opportunity cost of holding money instead of bonds, so higher interest rates mean people hold less money. Changes in income or the price level shift the entire money demand curve, while changes in the interest rate cause movements along it.
Money demand
The amount of money a person or firm wishes to hold outside any interest-bearing account at a given moment. In simple terms, it is how much wealth you keep as cash or in a non-interest-bearing chequing account rather than putting it into bonds or savings.
Nonsynchronisation of income and spending
The mismatch between when money arrives (e.g. a monthly pay cheque) and when it must be spent (e.g. rent due mid-month, groceries throughout the month). Think of it as the reason you need a cash buffer: your bills do not line up neatly with your pay days.
Optimal money balance
The amount of money holdings that minimises the combined cost of forgone interest (from not holding bonds) and transaction costs (fees or effort of converting bonds to cash). In simple terms, it is the sweet spot where you are not losing too much interest and not paying too many fees to cash out bonds.
Opportunity cost of holding money
The interest income you give up by keeping wealth as money rather than in an interest-bearing asset such as a bond. When interest rates are high, holding money costs you more in forgone earnings.
Transaction motive
The reason people hold money to pay for day-to-day purchases. Driven by the volume of transactions, income and the price level. Think of it as keeping cash in your wallet because you need to buy things.
Speculative motive
The reason people hold money based on their expectations about future interest rates and bond prices. If you expect interest rates to rise (and bond prices to fall), you hold money now so you can buy bonds later at a lower price. Think of it as a "wait and see" strategy.
Bond price and interest rate (inverse relationship)
When market interest rates rise, the price of existing bonds falls, and vice versa. This is because a bond's fixed payment becomes less attractive relative to new, higher-yielding alternatives.
Your money demand is whatever you keep outside interest-bearing accounts: cash in hand, current account balances.
If Sally earns $2,000 per month, deposits $500 in savings and buys $200 of government securities, her money demand is $1,300 (the remainder she keeps liquid for spending).
Income typically arrives in lumps (monthly salary), but spending happens continuously.
A person paid on the 1st whose rent is due on the 15th faces nonsynchronisation: they must hold money across the gap.
If you spend at a constant rate and your balance reaches $0 at month's end, your average balance is half your starting balance.
Starting balance $1,500 → average balance $750.
Starting balance $2,000 → average balance $1,000.
Starting balance $600, 30-day month → daily spending = $600 / 30 = $20/day.
Holding all your income as money means zero transaction costs but maximum forgone interest.
Switching some money into bonds earns interest but incurs transaction costs each time you sell a bond.
The optimal balance is where the marginal interest earned from one more switch just equals the cost of that switch.
A higher interest rate raises the opportunity cost of holding money, so the optimal balance falls.
Lower switching costs (cheaper brokerage, online transfers) also reduce the optimal balance.
Interest rate rises → optimal money balance decreases (it costs more to hold money).
Interest rate falls → optimal money balance increases (less incentive to park funds in bonds).
Switching costs fall → optimal money balance decreases (easier to convert bonds to cash).
Transaction volume or income rises → optimal money balance increases (more spending to cover).
Bond prices and interest rates are negatively related.
A bond that pays a fixed dollar amount becomes worth less when market rates rise, because investors can get a better return elsewhere.
Calculation pattern: if a bond was bought at $16,000 paying 5% ($800/year) and the market rate doubles to 10%, the bond's market price drops to $8,000 (because $800 is 10% of $8,000).
Conversely, if rates halve, bond prices double.
Transaction demand depends on aggregate income, the price level and the dollar value of transactions. It does not depend directly on the interest rate.
Speculative demand is negatively related to the interest rate. When rates are low (and expected to rise), people hold more money; when rates are high (and expected to fall), people hold bonds in anticipation of capital gains.
The transaction motive shifts the money demand curve (because it responds to income/prices). The speculative motive causes movements along the curve (because it responds to the interest rate).
The money demand curve slopes downward: lower interest rates → higher quantity of money demanded.
A movement along the curve is caused by a change in the interest rate.
A shift of the entire curve is caused by a change in income, the price level or the volume of transactions.
Increase in income or price level → curve shifts right (more money demanded at every interest rate).
Decrease in income or price level → curve shifts left.
Average balance (constant spending, balance reaches zero):
Average balance = Starting balance / 2
Daily spending rate:
Daily spending = Starting balance / Number of days in month
Bond pricing shortcut (simple fixed-payment bond):
Bond price = Annual payment / Market interest rate
Example: $800 annual payment, 10% market rate → $800 / 0.10 = $8,000.
The reason banks and fintech apps compete to make transfers instant and free is that lower switching costs reduce your optimal money balance. When moving money between a savings account and a current account is costless, people keep less idle cash and earn more interest, which is the practical version of the optimal-balance theory in this chapter.
Students often confuse money demand with income. Money demand is how much wealth you choose to hold as money, not how much you earn.
Students sometimes think a higher interest rate increases money demand. The opposite is true: higher rates raise the opportunity cost of holding money, so people hold less.
Students frequently think bond prices and interest rates move in the same direction. They move in opposite directions, always.
Students mix up movements along the curve with shifts of the curve. Interest rate changes cause movements; income or price level changes cause shifts.
⚠️ Know the difference between a shift of the money demand curve (income, price level, transactions) and a movement along it (interest rate change).
⚠️ Be able to calculate average balances, starting balances and daily spending rates from the information given.
⚠️ The bond-price calculation (annual payment / market interest rate) appears regularly. Practise both directions: rates rising and rates falling.
⚠️ Remember that the speculative motive moves you along the curve, while the transaction motive shifts it.
True or false: Money demand is the amount of money you wish to earn per month.
False. It is the amount you wish to hold outside interest-bearing accounts.
If your starting balance is $1,800 and you spend evenly until you reach $0, your average balance is ________.
$900.
True or false: An increase in the interest rate shifts the money demand curve to the left.
False. It causes a movement along the curve (upward/left along the same curve), not a shift.
If a bond pays $600 per year and the market interest rate is 5%, the bond's price is ________.
$12,000.
Fill in the blank: Bond prices and interest rates are ________ related.
Negatively.
Q: Sally earns $2,000 per month, deposits $500 in savings, buys $200 in government securities and keeps the rest for daily transactions. What is her money demand?
A: $1,300. Money demand is the portion held outside interest-bearing accounts: $2,000 − $500 − $200 = $1,300.
Q: Derek's average monthly balance is $750 and his balance reaches $0 at the end of the month. What is his starting balance?
A: $1,500. Since average balance = starting balance / 2, the starting balance is $750 × 2.
Q: Derek's average balance is $300 in a 30-day month, and his balance reaches $0. How much does he spend per day?
A: $20. Starting balance = $600; daily spending = $600 / 30 = $20.
Q: Jimmy bought a 5% bond for $16,000. The market interest rate has risen to 10%. What is the maximum price Jimmy can charge to sell the bond?
A: $8,000. The bond pays $800/year ($16,000 × 5%). At 10%, the price is $800 / 0.10 = $8,000.
Q: What happens to the optimal money balance when the interest rate increases?
A: It decreases, because the opportunity cost of holding money has risen.
Q: Which motive for holding money is negatively related to the interest rate?
A: The speculative motive.
Q: What causes the money demand curve to shift to the right?
A: An increase in income, an increase in the price level, or an increase in the volume of transactions.
This connects to the money supply material in Chapter 10: supply and demand together determine the equilibrium interest rate, which is covered in Part 2 of these notes. The equilibrium interest rate then feeds into planned investment and aggregate expenditure (Chapters 8-9), so this is the bridge between monetary policy and real economic output.
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