Interest Rate Effect vs Net Export Effect
Interest Rate Effect and Net Export Effect are two Aggregate Demand & Supply concepts in AP Economics that students often mix up. The interest rate effect is the change in investment that results from a change in the interest rate due to a change in the price level. The net export effect is the change in net exports that results from a change in the price level. Here is how they compare side by side.
When the price level rises, people need more money to buy goods and services. This increases the demand for money, which leads to an increase in the interest rate. Higher interest rates discourage borrowing and investment, leading to a decrease in aggregate demand. Conversely, when the price level falls, the interest rate decreases, leading to an increase in investment and aggregate demand.
When the price level rises in a country, its goods and services become more expensive relative to foreign goods and services. This leads to a decrease in exports and an increase in imports, causing net exports to fall. Conversely, when the price level falls, net exports rise as exports increase and imports decrease.
Interest Rate Effect vs Net Export Effect: Two Doors Out of a Higher Price Level
| Interest Rate Effect | Net Export Effect | |
|---|---|---|
| Component of AD it moves | Investment, plus interest-sensitive consumption such as housing and cars | Net exports, meaning exports minus imports |
| First link in the chain | A higher price level makes households and firms need more money for the same transactions | A higher domestic price level makes home-produced goods dearer relative to foreign goods |
| Middle of the chain | Money demand rises against a fixed money supply, so the interest rate is bid up | Buyers on both sides switch toward the cheaper foreign goods |
| Final step | Borrowing costs more, so firms buy less capital and fewer houses are built | Exports fall, imports rise, and net exports shrink |
| Market it runs through | The money market | Goods markets, and in many treatments the foreign exchange market as well |
| What makes it large | Investment that responds sharply to interest rates | An economy where trade is a large share of output |
| Who feels it first | Domestic borrowers, builders and firms planning capital projects | Exporters, import-competing firms and trading partners |
Both start at the price level, then leave through different markets
Two of the three reasons the AD curve slopes down are these, and they share only their starting point. Begin with a rise in the overall price level. The interest rate effect runs through the money market. Households and firms need more money to carry out the same real transactions, so the demand for money rises. With the money supply unchanged, the interest rate is bid up. Borrowing to build a plant or buy a house costs more, investment spending falls, and interest-sensitive consumption falls with it. The net export effect runs through trade. When domestic prices rise while foreign prices sit still, goods made at home become relatively expensive. Domestic buyers switch toward imports, foreign buyers pull back from exports, and net exports drop. Several textbooks add an exchange rate link on top: the higher interest rate attracts financial inflows, the currency appreciates, and the appreciation deepens the fall in net exports. Both versions land in the same place. Each effect lowers the quantity of real output demanded when the price level rises, which is what gives AD its slope instead of leaving it flat. Neither is a shift, because the price level is on the axis. The money market side is developed at /macro/monetary-policy.
Their relative size depends on borrowing and on how open the economy is
Take an illustrative economy, with figures chosen for the arithmetic rather than measured from data. The price index rises from 100 to 110. Higher interest rates cut planned investment by 30 billion dollars. Relative price changes cut net exports by 10 billion dollars. The initial fall in planned spending is therefore 40 billion dollars. That is not where it stops, because the households and firms who lose that income cut their own spending in turn. With a marginal propensity to consume of 0.75 the multiplier is 4, so the gap between the two quantities on the AD curve is roughly 160 billion dollars. The curve is drawn with those induced rounds already included, which is part of why AD is flatter than a single firm's demand curve. The split between the two channels is not fixed. In a large economy where trade is a small share of output, the interest rate channel usually does most of the work. In a small economy that trades heavily, the net export channel can be the larger of the two. The third reason for the slope, the wealth effect at /glossary/wealth-effect, works on consumption through the real value of money balances.
Frequently asked questions
What is the difference between the interest rate effect and the net export effect?
The interest rate effect reduces investment when a higher price level raises money demand and pushes interest rates up, while the net export effect reduces net exports when a higher domestic price level makes home-produced goods relatively expensive. One works through the money market and one works through trade. Both reduce the quantity of real output demanded.
Do the interest rate and net export effects shift the AD curve?
No, they explain why the AD curve slopes downward, so they produce movements along the curve rather than shifts of it. A shift requires a change in planned spending at an unchanged price level. Both of these effects are triggered by the price level itself.
Why does a higher price level reduce net exports?
A higher domestic price level makes goods produced at home more expensive compared with foreign goods, so foreign buyers purchase fewer exports and domestic buyers purchase more imports. Net exports are exports minus imports, so both movements push the total down. Many textbooks add that higher domestic interest rates strengthen the currency, which reinforces the same result.
Live AD/AS Model graph. Drag the curves, or open the full version.
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