The four channels a policy travels through
Why a policy aimed at one issue changes the others
- A government policy enters the economy at one point — a borrowing rate, a spending programme, a rule, a tariff.
- The effect does not stay there. It travels along a small number of channels, and each channel delivers it to a different economic issue.
- There are four channels, and every flow-on effect in Level 2 Economics runs down one of them. Knowing which channel a policy is using tells you which issue it will land on and which model draws it.
Channel 1 — the interest-rate channel, into aggregate demand
- How it works: the OCR changes → banks reprice mortgage, business lending and deposit rates → borrowing becomes dearer or cheaper → households spend less or more () and firms finance fewer or more projects ().
- Since , aggregate demand shifts, moving the price level and real GDP together.
- Model: AS/AD.
- Issues it lands on: inflation and economic growth.
- Fiscal policy uses the same channel by a different door: and taxation change AD directly, without waiting for banks to reprice anything.
Channel 2 — the exchange-rate channel
- How it works: New Zealand interest rates rise relative to overseas → overseas investors want New Zealand assets → they must buy NZ$ to do it → demand for NZ$ shifts right → the NZ$ appreciates from Er to Er1.
- An appreciation makes New Zealand exports dearer in foreign currency, so volumes fall and each unit earns fewer NZ$: falls. It makes imports cheaper in New Zealand dollars: rises. The balance on goods and services worsens.
- Model: the market for the NZ$, then the two-country or price taker model for the trade effect itself.
- Issue it lands on: international trade.
The exchange rate is a channel, not an issue.
- The contemporary economic issue is international trade. The exchange rate is the route the policy took to get there.
- Writing "the flow-on effect is on the exchange rate" names the corridor instead of the room. Name the issue, then use the exchange rate to explain how the policy reached it.
Channel 3 — the cost channel, into aggregate supply
- How it works: anything that changes firms' costs of production shifts AS.
- Compliance costs, taxes on production and tariffs on imported inputs raise costs → AS shifts left → price level up, real GDP down.
- Deregulation, cheaper imported inputs, infrastructure and training lower costs or raise productivity → AS shifts right → price level down, real GDP up.
- Model: AS/AD, with the PPF for the capacity effect.
- Issues it lands on: inflation and economic growth — but in the opposite combination to channel 1.
- This is why supply-side policy is so useful. Channel 1 trades inflation against growth; channel 3 moves both in a direction the economy wants at once.
Channel 4 — derived demand, into the labour market
- How it works: firms hire workers because of what those workers produce and sell, so labour demand is derived demand.
- Output demand falls → firms sell less → they need fewer workers → DL shifts left from DL to DL1 → the wage falls from We to We1 and employment falls from Le to Le1.
- Model: labour market supply and demand, plus the PPF, where unemployment is the economy sitting at a point inside its frontier.
- Issue it lands on: unemployment.
- This channel is always second-hand. Nothing reaches the labour market directly — it arrives only after channel 1 or channel 3 has changed how much firms are producing.
Which model draws which channel
| Channel | Model to draw | Issue it lands on |
|---|---|---|
| Interest rate → AD | AS/AD | Inflation, economic growth |
| Exchange rate | Market for the NZ$, then two-country or price taker | International trade |
| Cost → AS | AS/AD, plus the PPF | Inflation, economic growth |
| Derived demand | Labour market, plus the PPF | Unemployment |
The channels do not arrive at the same time
- The exchange rate moves first — within days. Currency markets reprice the moment the OCR decision is announced, and sometimes before, on the expectation of it.
- Aggregate demand moves over quarters. Households on fixed-rate mortgages feel nothing until they refix; firms' investment decisions were made months ago.
- The labour market moves later still — two to three quarters after output. Firms cut hours and stop replacing leavers before making anyone redundant, and raise existing staff's hours before hiring.
- Capacity moves over years. Infrastructure, training and research change AS and the PPF long after the money is spent.
What follows from that.
- A policy can look as though it is failing when only its fast channels have arrived. A higher OCR that has squeezed exporters through the currency but not yet cooled the price level is a policy working normally, not a policy that has not worked.
- Judging a policy against data from the same quarter judges it before most of it has happened.
Two channels can pull against each other
- A higher OCR reaches inflation twice, and both routes lower the price level: AD shifts left (channel 1), and the appreciation makes imported goods and inputs cheaper, shifting AS right (channels 2 and 3 together).
- But on real GDP the same two channels conflict. AD left lowers Y; AS right raises it. The net effect on growth is the difference between them, and the AD effect is normally much the larger — which is why a higher OCR reduces growth rather than raising it.
- Saying which channel dominates, and why, is the difference between listing effects and explaining one.
Worked ExampleOne policy, four channels
Inflation has fallen back inside the RBNZ's 1–3% target band and the economy is weak. The RBNZ cuts the OCR.
Trace the cut down each of the four channels, name the issue each one lands on, and say how fast each arrives.
Step 1 — Channel 1: the interest-rate channel, into aggregate demand
Banks reprice mortgage, business lending and deposit rates downward. Borrowing is cheaper, so households bring forward spending ( rises) and firms find more investment projects worth financing ( rises).
Since , aggregate demand shifts right from AD to AD1. Against the unchanged AS curve, real GDP rises from Y to Y1 and the price level rises from PL to PL1.
Issue it lands on: economic growth — positively. And inflation — this is the cost of the cut, and the reason the RBNZ waited until inflation was back inside the band.
Speed: several quarters. Households on fixed-rate mortgages feel nothing until they refix, so the spending response builds gradually.
Step 2 — Channel 2: the exchange-rate channel
New Zealand interest rates are now lower relative to overseas, so New Zealand assets are less attractive to overseas investors. Demand for NZ$ shifts left, and the NZ$ depreciates from Er to Er1.
New Zealand exports become cheaper in foreign currency, so overseas buyers buy more and volumes rise; exporters also receive more NZ$ for each unit of foreign currency earned. Export receipts ($X$) rise on both dimensions. Imports become dearer in New Zealand dollars, so import payments () fall. The balance on goods and services improves.
Issue it lands on: international trade — positively. Note that the exchange rate is how the policy got there, not the issue itself.
Speed: immediate. Currency markets move on the announcement, and often on the expectation of it beforehand.
Step 3 — Channel 3: the cost channel, into aggregate supply
The depreciation raises the New Zealand dollar cost of imported fuel, machinery, materials and components. Firms' costs of production rise, so they supply less at every price level: AS shifts left from AS to AS1, raising the price level further and pulling real GDP back a little.
Cheaper borrowing partly offsets this, because interest is a cost for firms carrying debt and cheaper finance makes capacity-raising investment viable — an AS right effect that arrives much later.
Issue it lands on: inflation — negatively, and this compounds the inflation effect already coming from channel 1.
Speed: the imported-cost effect arrives over quarters, as existing supply contracts and inventories are used up. The capacity effect takes years.
Step 4 — Channel 4: derived demand, into the labour market
Firms are now selling more, because AD rose in channel 1 and exports rose in channel 2. Because labour demand is derived demand, producing more requires more labour: DL shifts right from DL to DL1, the wage rises from We to We1 and employment rises from Le to Le1.
On the PPF, the economy moves from a point inside the frontier back toward it — the idle workers are put back to work, so this is a recovery of cyclical unemployment, not an increase in capacity.
Issue it lands on: unemployment — positively.
Speed: two to three quarters after output responds, so the slowest of the four. Firms first restore the hours they had cut, then hire.
Step 5 — Put the four together
| Channel | Issue | Direction | Model | Arrives |
|---|---|---|---|---|
| Interest rate → AD | Growth (+), inflation (−) | AD right | AS/AD | Quarters |
| Exchange rate | International trade (+) | NZ$ depreciates | Market for NZ$ | Days |
| Cost → AS | Inflation (−) | AS left | AS/AD, PPF | Quarters, then years |
| Derived demand | Unemployment (+) | DL right | Labour market, PPF | 2–3 quarters after output |
Reading the table. Three of the four channels are working in the direction the RBNZ wants — growth up, trade improving, employment up. Inflation is hit twice in the unwanted direction, once by the AD shift and once by the cost of imports after the depreciation.
That is the whole trade-off in one cut: the same depreciation that helps exporters raises imported costs, and the same demand stimulus that creates jobs raises prices. Whether the cut is right depends on how far inflation is below the top of the band and how much spare capacity the economy has — because with plenty of idle resources, the AS curve is flat and most of the extra demand becomes output rather than prices.