Money demand explains how much wealth people choose to hold as money rather than interest-earning assets. The key idea is that the nominal interest rate measures the opportunity cost of holding money.

Core relationship: money demand and the nominal interest rate

What “money demand” means

People hold money because it is liquid and readily usable for payments, but most money balances earn little or no interest. Money demand is therefore a choice about portfolio allocation between money and other financial assets.

In the money market model, the nominal interest rate is the key “price” that influences this choice.

Why the relationship is inverse

The inverse relationship comes from opportunity cost:

• When the nominal interest rate rises, the return on non-money assets (such as interest-bearing accounts, bonds, or other short-term instruments) is higher.

• Holding money then means giving up more interest income, so people reduce the quantity of money they want to hold.

• When the nominal interest rate falls, the opportunity cost of holding money is lower, so people are more willing to hold larger money balances.

This logic is often described as a trade-off between liquidity and return: money is highly liquid, but typically low return; other assets are less liquid, but higher return.

Representing money demand

In a standard graph of the money market, the money demand curve slopes downward: as the nominal interest rate on the vertical axis increases, the quantity of money demanded on the horizontal axis decreases.

Money-market equilibrium diagram with the nominal interest rate on the vertical axis and real money balances on the horizontal axis. The downward-sloping liquidity preference (money demand) curve intersects a vertical real money supply curve, pinning down the equilibrium interest rate. This visual reinforces why higher nominal interest rates reduce the quantity of money demanded. Source

The curve summarises many individual decisions:

• Households adjusting how much they keep in checking accounts versus moving funds into interest-earning alternatives

• Firms adjusting cash balances for payroll and purchases versus holding more in interest-bearing accounts

The notation $L(i)$ emphasises that desired money holdings depend negatively on $i$ (an inverse relationship).

Intuition: what changes when interest rates change?

Substitution away from money when rates rise

When $i$ increases, people tend to:

• Minimise idle balances (keep less in non-interest-earning form)

• Shift into interest-bearing assets (even if they are slightly less liquid)

• Use cash-management tools more actively (timing payments and deposits) to reduce average balances

This is not about spending more or less overall; it is about the form in which wealth is held.

Greater willingness to hold money when rates fall

When $i$ decreases, people tend to:

• Keep larger precautionary balances because the foregone interest is smaller

• Avoid the hassle/costs of frequently moving funds across accounts

• Hold more money for convenience, since the “penalty” from lost interest is low

Key AP interpretation points

“Ceteris paribus” is essential

The inverse relationship is stated holding other factors constant. The money demand curve captures how money holdings change when only the nominal interest rate changes, not when other determinants change.

Money demand is about desired holdings, not actual money supply

Money demand describes what people want to hold at each interest rate. If people want to hold less money at a higher interest rate, they try to exchange money for other assets, which influences asset prices and yields until the interest rate is consistent with desired money holdings.

Why AP uses the nominal (not real) interest rate here

The opportunity cost of holding money is tied to the nominal return available on alternative assets in financial markets. A rise in the nominal interest rate increases the interest income forgone by holding money, strengthening the incentive to reduce money balances.