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IAI Actuarial Core Principles · Business Economics

Impact of Advertising on Sales and Demand

Advertising aims to shift a firm's demand curve right, make it less elastic, or both. You measure the effect with advertising elasticity, the % change in sales for a 1% change in advertising. A profit-maximising firm sets advertising using the Dorfman-Steiner rule: advertising-to-sales ratio equals advertising elasticity ÷ price elasticity magnitude.

What this chapter covers

This chapter asks one question: what does a rupee spent on advertising do to demand, and how much should a firm spend? You start with the types and aims of advertising, then link them to the demand curve. Advertising can shift demand outwards, change its slope, or make buyers less sensitive to price.

The middle of the chapter is quantitative. You define advertising elasticity of demand and combine it with price elasticity to find the optimal advertising budget using the Dorfman-Steiner condition. This is the part most likely to give calculation marks.

The last topic widens the view. You ask how advertising behaves under different market structures, such as monopolistic competition and oligopoly, and whether it helps or harms consumers and welfare. This connects to the Microeconomics part of CB2, which carries 40% of the 2026 syllabus weighting (Macroeconomics carries 55%), and to elasticity, market power and pricing. Written answers often ask you to combine a calculation with a discussion.

CB2 mixes multiple-choice questions with written questions, and this chapter suits both. Definitions and the effect on the demand curve can come as quick MCQs. The Dorfman-Steiner rule and elasticity links give short calculation marks, and the welfare debate gives discussion marks where a balanced argument scores well. Because the chapter builds on elasticity and market structure, studying it also strengthens other microeconomics topics. The pass mark for CB2 is at least 50%, so reliable marks from a compact chapter help.

Impact of advertising on sales and demand: topics in the order to study them

  1. 1Types and Objectives of AdvertisingStart with the vocabulary: informative versus persuasive advertising, and what firms want from it, so later models make sense.
  2. 2Advertising and the Demand CurveNext, see how advertising shifts or rotates demand and changes price sensitivity, which sets up the elasticity ideas.
  3. 3Advertising Elasticity and Sales ResponseOnce you know the direction of the effect, learn to measure it with advertising elasticity and sales response.
  4. 4Optimal Advertising Spending (Dorfman-Steiner)This needs both price elasticity and advertising elasticity, so it comes after you have mastered the measures.
  5. 5Advertising, Market Structure and WelfareFinish with the broader evaluation, since you can argue it best once you understand the mechanics and the optimal rule.

How to prepare Impact of advertising on sales and demand

Treat this as a short chapter with one core formula and one core debate. Balance understanding with practice, and keep your notes short enough to revise on a phone.

  1. Write a one-line definition for each type of advertising and each objective, with an example from Indian markets such as FMCG or telecom.
  2. Draw the demand curve three ways: a rightward shift, a rotation to be steeper, and both together. Label what each means for price and quantity.
  3. Define advertising elasticity as % change in quantity ÷ % change in advertising, and practise computing it from given data. State the assumption that other factors stay constant.
  4. Learn the Dorfman-Steiner condition: A ÷ (P × Q) = advertising elasticity ÷ |price elasticity|. Practise rearranging it to find spend or the ratio, and check units.
  5. Prepare a two-sided argument on welfare: information and competition benefits versus entry barriers and wasteful spending. Link each to a market structure.
  6. Finish with mixed past-style questions: a few MCQs on definitions and signs, then one written question that combines a calculation with a short evaluation.

Common mistakes in Impact of advertising on sales and demand

  • Confusing a shift of the demand curve with a movement along it.

    Fix: Say it explicitly: price change moves along the curve, advertising shifts or rotates the curve.

  • Using the signed price elasticity in the Dorfman-Steiner rule and getting a negative ratio.

    Fix: Use the magnitude |price elasticity|, or write the rule as A ÷ (P × Q) = −(advertising elasticity ÷ price elasticity) so the result is positive. Check that the ratio is positive and, as a share of revenue, normally well below 1.

  • Mixing up the ratio with the spend amount.

    Fix: Multiply the ratio by sales revenue (P × Q) to get the amount. Write the units next to each answer.

  • Treating advertising elasticity as constant and unlimited.

    Fix: Note that the elasticity applies to small changes around the current level, and mention diminishing returns when you evaluate.

  • Giving a one-sided welfare answer.

    Fix: Give at least one benefit and one cost, tie each to a market structure, and end with a short judgement.

  • Skipping assumptions in written answers.

    Fix: State profit maximisation, other factors constant and the elasticity values used before you calculate.

Last-day revision: Impact of advertising on sales and demand

  • Informative advertising gives facts; persuasive advertising tries to change preferences and build brand loyalty.
  • Advertising aims to raise demand, reduce price elasticity, build loyalty, or deter entry.
  • Successful advertising shifts the demand curve to the right at each price.
  • It can also make demand less elastic, which lets the firm raise price.
  • Advertising elasticity = % change in quantity demanded ÷ % change in advertising expenditure.
  • Dorfman-Steiner: advertising spend ÷ sales revenue = advertising elasticity ÷ |price elasticity|.
  • The rule assumes the firm maximises profit and that price elasticity is measured as a magnitude.
  • Higher advertising elasticity or less elastic demand means a higher optimal advertising-to-sales ratio.
  • Advertising has diminishing returns, so extra spend adds less and less to sales.
  • Advertising is most important where products are differentiated, such as monopolistic competition and oligopoly.
  • Welfare effects are mixed: more information and choice versus higher prices, barriers to entry and waste.
  • State your assumptions in written answers and show each step of the working.

Impact of advertising on sales and demand practice questions

Impact of advertising on sales and demand in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Impact of advertising on sales and demand: frequently asked questions

What is advertising elasticity of demand?

It is the % change in quantity demanded divided by the % change in advertising expenditure, holding other factors constant. A positive value means more advertising raises sales. A larger value means sales respond more strongly.

What is the Dorfman-Steiner condition in simple words?

It says a profit-maximising firm should spend on advertising until the advertising-to-sales ratio equals advertising elasticity divided by the magnitude of price elasticity. So firms with more responsive sales or less price-sensitive buyers spend a bigger share of revenue on advertising.

Does advertising always shift the demand curve right?

No. Successful advertising is meant to, but it may also make demand less elastic or only defend existing sales against rivals. In competitive markets the effects can partly cancel out.

How should I answer a welfare question on advertising?

Give both sides. Benefits include information and support for competition; costs include higher prices, entry barriers and wasted resources. Link your points to the market structure in the question and finish with a short conclusion.