The Core Idea
Using Elasticity to Predict Revenue, Not Just Quantity
The Price Elasticity lesson established HOW MUCH quantity demanded responds to a price change. The total revenue test takes this one step further, using elasticity to predict something genuinely practical for a business: will raising or lowering price actually INCREASE total revenue (price × quantity), or decrease it?
The key insight is that a price change has TWO competing effects on revenue that pull in opposite directions: raising price increases revenue PER UNIT sold, but (per the Law of Demand) also decreases the NUMBER of units sold — which effect wins depends entirely on elasticity.
💡 Memory Trick
Picture total revenue as a rectangle on a demand curve graph, with price as the height and quantity as the width — raising price makes the rectangle TALLER but also NARROWER (since quantity falls). If demand is ELASTIC, quantity shrinks by a LARGER percentage than price grows, so the rectangle's area (total revenue) actually SHRINKS overall — the narrowing effect wins. If demand is INELASTIC, quantity shrinks by a SMALLER percentage than price grows, so the rectangle's area GROWS overall — the heightening effect wins.
The Three Cases
How Price Changes Affect Revenue Under Each Elasticity
1
Elastic Demand (PED > 1)
Raising price DECREASES total revenue, since the percentage drop in quantity demanded exceeds the percentage increase in price — the narrowing effect on the revenue rectangle outweighs the heightening effect. Conversely, LOWERING price INCREASES total revenue for an elastic good, since the resulting percentage increase in quantity sold more than compensates for the lower per-unit price.
2
Inelastic Demand (PED < 1)
Raising price INCREASES total revenue, since the percentage drop in quantity demanded is smaller than the percentage increase in price — the heightening effect on the revenue rectangle outweighs the narrowing effect. Conversely, LOWERING price DECREASES total revenue for an inelastic good, since the modest increase in quantity sold doesn't compensate for the lower per-unit price.
3
Unit Elastic Demand (PED = 1)
A price change leaves total revenue UNCHANGED, since the percentage change in quantity demanded exactly offsets the percentage change in price — the heightening and narrowing (or widening) effects on the revenue rectangle exactly cancel out.
Why This Matters for Real Pricing Decisions
A Direct, Practical Application of Elasticity
This is one of the most immediately practical applications of the entire elasticity framework: a business deciding whether to raise or lower prices should first estimate whether its product's demand is elastic or inelastic — a firm selling a good with elastic demand (many substitutes, discretionary purchase) should generally be cautious about price increases, since they'd likely REDUCE total revenue, while a firm selling a good with inelastic demand (few substitutes, necessity) can often successfully raise prices to increase total revenue.
This connects to why firms with genuine market power (like Monopoly, from the Market Structures sub-subject) generally avoid setting prices in the elastic region of their demand curve — doing so would mean they could increase revenue AND reduce output simultaneously by raising price slightly, an obviously better outcome, which is exactly why a profit-maximizing monopolist rationally never operates on the elastic-losing side of this trade-off.
🖥️ Applied Scenario
A coffee shop is considering raising prices by 10%, and needs to predict whether this will increase or decrease total revenue, given that coffee shop lattes have an estimated PED of 1.8 (elastic, since there are many nearby coffee shop substitutes).
1
You identify PED = 1.8, which is greater than 1, meaning demand for this specific coffee shop's lattes is ELASTIC — customers can easily switch to a nearby competitor if prices rise.
2
You apply the total revenue test: for elastic demand, raising price DECREASES total revenue, since the percentage drop in quantity sold (as customers switch to competitors) will exceed the percentage increase in price.
3
You recommend AGAINST the 10% price increase, since it would likely reduce total revenue rather than increase it, given the elastic nature of demand for this specific product in this specific competitive local market.
4
Conclusion: correctly applying the total revenue test — rather than assuming a price increase automatically increases revenue — reveals that this specific pricing decision would actually backfire, given the estimated elasticity of demand for this good in this market.
📌 Exam Application
Exam questions frequently give you a PED value (or a description implying elastic/inelastic demand) and ask you to predict whether raising or lowering price would increase or decrease total revenue. You may also be asked to explain why a profit-maximizing firm with market power would never set a price in the elastic portion of its own demand curve.
⚠️ Most Common Total Revenue Test Mistakes
The most common mistake is assuming raising price ALWAYS increases total revenue — this is only true when demand is INELASTIC; for ELASTIC demand, raising price actually DECREASES total revenue, since the resulting drop in quantity sold outweighs the higher per-unit price. Another frequent error is forgetting the unit elastic case entirely — when PED equals exactly 1, a price change (in either direction) leaves total revenue completely unchanged, a specific boundary case that's easy to overlook when focusing only on the elastic and inelastic scenarios.
✓ Quick Self-Test
Given a PED value (or elastic/inelastic classification), can you correctly predict whether raising price would increase, decrease, or leave total revenue unchanged? Can you explain, using the total revenue test, why a profit-maximizing firm would never set its price in the elastic region of its demand curve?
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