PES measures how much the quantity supplied of a good changes when its price changes. It tells us whether producers are quick or slow to respond to price shifts.
The elasticity is calculated as:
\$Es = \dfrac{\% \Delta Qs}{\% \Delta P}\$
Where \$\% \Delta Q_s\$ is the percentage change in quantity supplied and \$\% \Delta P\$ is the percentage change in price.
If \$Es > 1\$, supply is elastic (responsive). If \$Es < 1\$, supply is inelastic (unresponsive). If \$E_s = 1\$, supply is unit‑elastic.
| Factor | Effect on PES | Why? |
|---|---|---|
| Time Horizon | Longer time → higher PES | Firms can adjust production, hire workers, buy equipment. |
| Availability of Inputs | More inputs → higher PES | Easy to increase output when resources are plentiful. |
| Production Technology | Advanced tech → higher PES | Faster, cheaper, and more flexible production. |
| Capacity Constraints | Limited capacity → lower PES | Cannot increase output beyond existing limits. |
| Substitutability of Products | High substitutability → higher PES | Firms can switch easily between products. |
| Regulatory / Policy Constraints | Strict regulations → lower PES | Extra costs or limits on production. |
Imagine a pizza shop. If the price of pizza rises, the shop can quickly add more ovens (if they have spare capacity) and hire more chefs. This quick response means a high PES. But if the shop already has the maximum number of ovens and no spare space, it cannot increase output even if the price jumps. That’s a low PES.
Another example: A farmer’s wheat supply is inelastic in the short run because the land and equipment cannot be changed quickly. In the long run, the farmer can buy more land or invest in better machinery, making supply more elastic.
- PES = \$\dfrac{\% \Delta Q_s}{\% \Delta P}\$
- Elastic (Es > 1): producers respond quickly.
- Inelastic (Es < 1): producers respond slowly.
- Key factors: time, inputs, technology, capacity, substitutes, regulation.