Price elasticity of supply

Price-elastic supply is where a change in price causes a proportionally larger change in quantity supplied (1), so the price elasticity of supply is greater than 1 and producers can change their output easily in response to price (1).

% change in quantity supplied: (260 − 200) ÷ 200 × 100 = +30% (1). % change in price: (60 − 50) ÷ 50 × 100 = +20% (1). PES = %ΔQ ÷ %ΔP = 30 ÷ 20 = +1.5 (1). Because PES = 1.5 > 1, supply is price-elastic (1) — quantity supplied changed by a larger percentage than price.

Spare capacity. If a firm has unused capacity — idle machines and workers available — it can increase output quickly when the price rises, so quantity supplied changes by a large percentage and supply is elastic. If a firm is already at full capacity, it cannot easily produce more, so supply is inelastic. Ability to store the good. If a good is storable (such as grain or manufactured items), firms can build up stocks when prices are low and release them when prices rise, so quantity supplied responds strongly to price — supply is elastic. If a good is perishable (fresh fish, milk), it cannot be stored, so firms must sell what they produce regardless of price and cannot easily increase supply when prices rise — supply is inelastic. So spare capacity and storability both make supply more responsive to price; their absence makes supply inelastic.

The supply of fresh fish is likely to be price-inelastic for several connected reasons. First, it is highly perishable. Fresh fish cannot be stored for long, so fishermen must sell their catch quickly and cannot build up stocks to release when prices rise — quantity supplied therefore changes little when the price changes. Second, output cannot be quickly increased. Even if the price of fish rises, fishermen cannot easily catch more in the short run — they are limited by the size of their boats, the number of fishing days and fish stocks in the sea — so quantity supplied responds only a little. Third, expanding capacity takes time and resources (more boats, more crew), which cannot be done immediately. Because the good cannot be stored and output cannot be raised quickly, a price rise produces only a small percentage increase in quantity supplied, so the PES is less than 1 — supply is inelastic. Over the long run, with more boats, supply could become somewhat more elastic.

Making food supply more price-elastic has benefits but also costs, so it is debatable. Why a government might want to: if food supply is very inelastic, a poor harvest or a rise in demand causes large swings in price, which hurt consumers (sharp price rises for an essential) and make farmers' incomes unstable. Making supply more elastic — by helping farmers store crops, invest in technology, irrigation and better seeds — would mean output can respond more to price, keeping food prices and supplies more stable, which is good for an essential good. Why it might not be the best use of resources: doing this is expensive — subsidising storage, irrigation and technology has a large opportunity cost (the money could fund healthcare or education); some factors are hard to change (growing time, weather); and other measures, such as building food reserves or allowing imports, might stabilise food supplies more cheaply. Judgement: a government should try to make food supply more elastic to some extent, because stable food prices and supplies matter for citizens, especially the poor — but it should weigh this against the cost and consider cheaper alternatives like reserves or imports. So the policy is worthwhile if affordable and well-targeted, but it is not automatically the best way to stabilise food, which depends on the government's budget and the alternatives available.

Both elasticities affect a wheat farmer, so saying PES is more important is debatable. Why PES might be more important to the farmer: PES describes how easily the farmer can change output when the price changes. Because wheat takes a growing season to produce, supply is inelastic in the short run, so when prices rise the farmer cannot quickly produce more to take advantage — this directly affects the farmer's revenue and planning, so understanding it matters. Why PED matters as much or more: PED describes how consumers respond to price changes. Wheat (a staple) tends to have inelastic demand, which means that when supply changes — say a good harvest raises supply — the price falls sharply (because demand is unresponsive), and the farmer's revenue can actually fall despite producing more. So the farmer's income depends heavily on PED, not just PES. Judgement: both elasticities matter to a wheat farmer, and neither is simply more important. PES affects how the farmer can respond to prices, but PED strongly affects what happens to price and revenue when supply changes — and for a staple with inelastic demand, PED can be decisive (a bumper harvest can reduce income). So the farmer needs to understand both, and which is more important depends on the situation — making the claim that PES is more important impossible to accept as a general rule.