Exam Frequency Analysis
Past paper frequency (2018 to 2024)
This topic accounts for approximately 10% of your exam marks.
stable
Medium
Stable10%
PES definition, formula, calculation, and determinants appear on most papers; typically 4 to 6 marks paired with PED or market analysis questions.
Just like PED, supply can be sorted into five categories. Only the middle three appear in practical exam questions; the two extremes are theoretical.
| Category | Value of PES | What it means | Typical example |
|---|---|---|---|
| Perfectly inelastic | 0 | Qs is fixed; no responsiveness at all | A single Picasso painting; seats at a sold-out concert venue |
| Relatively inelastic | 0 < PES < 1 | %ΔQs is smaller than %ΔP | Most agricultural goods, oil in the short run |
| Unit elastic | PES = 1 | %ΔQs equals %ΔP | Any supply curve drawn passing through the origin |
| Relatively elastic | PES > 1 | %ΔQs is larger than %ΔP | Manufactured goods with spare factory capacity |
| Perfectly elastic | ∞ | Producers will supply any amount at the given price; supply is unlimited | Theoretical only |
The two values that matter on the exam: less than 1 = inelastic; greater than 1 = elastic. Memorise that and most PES questions resolve quickly.