Weak demand and weak productive capacity require different explanations.
Persistently weak real-output growth can arise from inadequate aggregate demand, adverse supply conditions or slow growth of productive capacity. Weaker foreign demand, cautious households or low expected investment returns can restrain spending. Poor infrastructure, skills gaps, disrupted inputs or weak productivity can constrain supply. A contraction can reduce employment, incomes and firms' sales; if prolonged, it may also discourage investment and erode skills, weakening future capacity. Low growth is not automatically undesirable at every moment: consider initial capacity use, population, sustainability and whether a slowdown follows overheating.
- Demand channel
- Aggregate demand (AD) is planned spending on domestic output: household consumption (C), investment (I), government purchases (G) and net exports. Net exports are sales abroad minus purchases from abroad. Weaker spending can leave usable resources idle.
- Supply channel
- Aggregate supply (AS) describes the output firms will produce at each general price level. Disrupted inputs, higher costs per unit or weak productivity can limit production. Productivity is output per unit of input, such as output per worker-hour.
- Longer-run damage
- If weak sales persist, firms may postpone new machinery and workers may lose skills through lack of use. These changes can reduce future productive capability as well as current output.
Why a slowdown can last
Households and firms
Weak employment and incomes can reduce consumption; weaker sales and expectations can discourage further investment.
Context
Overheating means spending presses against limited productive capacity, creating price pressure. Slower growth after overheating may ease that pressure. Its effects depend on starting conditions, duration, population and environmental limits.
Worked example: Fewer export orders and unreliable electricity
A trading economy loses overseas orders for two years. Factories have idle machines and firms postpone investment. Separately, repeated electricity outages interrupt production even when orders are available.
- Fewer export orders reduce AD and can lower output through demand deficiency while resources remain idle.
- Electricity outages restrict production or raise unit costs, creating a separate adverse AS channel.
- Lower sales can make new equipment seem less profitable, so firms postpone investment. That slows the addition of productive capital; long periods without work may also weaken workers' skills.
- Evidence on orders, capacity use, input reliability and productivity is needed to assess which constraint dominates. A growth headline alone cannot diagnose it.
Watch out for this
Every period of low growth is caused by consumers not spending enough.
Supply constraints and productivity weakness can also reduce growth. Causes can coexist and have different implications.
Check your understanding
Firms have many unfilled orders but cannot produce because of repeated power failures. Which constraint is most directly supported?
- A supply constraint.
- Proof that there is no demand for their output.
- Only frictional unemployment.