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Demand and Elasticity of Demand Kamal Singh Assistant Professor in Economics

Demand and Elasticity of Demand Kamal Singh Assistant Professor in Economics. Meaning of Demand. “The demand for anything, at a given price, is the amount of it, which will be bought per unit of time, at that price.” Benham

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Demand and Elasticity of Demand Kamal Singh Assistant Professor in Economics

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  1. Demand and Elasticity of Demand Kamal Singh Assistant Professor in Economics

  2. Meaning of Demand • “The demand for anything, at a given price, is the amount of it, which will be bought per unit of time, at that price.” Benham “By demand we mean the various quantities of a given commodity or service which consumers would buy in one market in a given period of time at various prices.” Bobber Requisites: • Desire for specific commodity. • Sufficient resources to purchase the desired commodity. • Willingness to spend the resources. • Availability of the commodity at • (i) Certain price (ii) Certain place (iii) Certain time.

  3. Kinds of Demand • Individual demand • Market demand • Income demand • Demand for normal goods (price –ve, income +ve) • Demand for inferior goods (eg., coarse grain) • 4. Cross demand • Demand for substitutes or competitive goods (eg.,tea & coffee, bread and rice) • Demand for complementary goods (eg., pen & ink) • 5. Joint demand (same as complementary, eg., pen & ink) • 6. Composite demand (eg., coal & electricity) • 7. Direct demand (eg., ice-creams) • 8. Derived demand (eg., TV & TV mechanics) • 9. Competitive demand (eg., desi ghee and vegetable oils) • 10.Demand of unrelated goods

  4. FACTORS AFFECTING DEMAND • Prices of Goods • Income of Consumer • Prices of Related Goods • Population • Tastes, Habit • Expectation about future prices • Climatic Factors • Demonstration Effect • Distribution of national income

  5. Demand Schedule • Demand Schedule: a tabular presentation showing different quantities of a commodity that would be demanded at different prices. • Types of Demand Schedules Individual Demand schedule Market Demand Schedule

  6. Demand Curve • The Graphical Representation of Demand Schedule is called a Demand Curve. It is of two types: Types of Demand Curve Y Y Price Less Flatter Price More Flatter O Demand X O Demand X Individual DC Market DC

  7. Demand Curve • Movement along demand curve Vs. Shift in demand curve: • Distinction between change in quantity demanded and change in demand. • A. Change in quantity demanded – When quantity demanded changes ( rise or fall ) as a result of change in price alone, other factors remaining the same. • Contraction/fall in quantity demanded • Extension/Rise in quantity demanded The change is depicted/ represented by the movement up or down on a given demand curve. This does not require drawing a new demand curve.

  8. Figure 2.2 Shifts in the demand curveAn increase in demand is represented by a rightward, outward, shift in the demand curve,from D1to D2. A decrease in demand is represented by a leftward, or inward, shift in thedemand curve, from D1 to D3.

  9. The Law of Demand • Prof. Samuelson: “Law of demand states that people will buy more at lower price and buy less at higher prices, others thing remaining the same.” • Ferguson: “According to the law of demand, the quantity demanded varies inversely with price”. • Chief Characteristics: • Inverse relationship. • Price independent and demand dependent variable. • Income effect & substitution effect. • Assumptions: • No change in tastes and preference of the consumers. • Consumer’s income must remain the same. • The price of the related commodities should not change. • The commodity should be a normal commodity

  10. A P P B D2 D1 Q Q The Law of Demand P1 P2 Q1 Q2 CHANGE IN PRICE= change in quantity demanded CHANGE IN OTHER= change in demand

  11. P D2 D1 Q The Law of Demand CHANGE IN OTHER= change in demand

  12. Determinants of Demand • Change in consumer tastes • Change in people’s income • normal goods • inferior goods • Change in Population • Change in Habits • Government Policies • Income distribution • Change in price of related goods • Consumer expectations with regard to future prices • Advertisement Expenditure

  13. Dx= a-bPx Dx= Demand for X commdity A= constant B= Slope Px= price of X commodity

  14. Why demand curve slopes downwards? 1. Income effect 2. Substitution effect 3. Diminishing Marginal Utility 4. Increase in number of consumer 5. Alternative uses

  15. Elasticity of demand • Definition: “Elasticity of demand is defined as the responsiveness of the quantity demanded of a good to changes in one of the variables on which demand depends.” • These variables are price of the commodity, prices of the related commodities, income of the consumer & other various factors on which demand depends. Thus, we have Price Elasticity, Cross Elasticity, Elasticity of Substitution & Income Elasticity. It is always price elasticity of demand which is referred to as elasticity of demand A. Price Elasticity Measures how much the quantity demanded of a good changes when its price changes. Or It may be defined as “Percentage Change in Quantity demanded over percentage change in price”

  16. Factors affecting Elasticity of Demand • Availability of substitutes • Postponement of consumption • Proportion of expenditure (needles: inelastic; TV: elastic) • Nature of the commodity (necessity vs. luxury; durability/reparability eg., shoes) • Different uses of the commodity (paper vs. ink) • Time period (elastic in the long term) • Change in income (necessaries: inelastic; milk and fruit for a rich man) • Habits • Joint demand • Distribution of income • Price level (very costly & very cheap goods: inelastic)

  17. Exceptions: • Inferior goods • Articles of snob appeal. (exception: Veblen goods, eg., diamonds) • Expectation regarding future prices (shares, industrial materials) • Emergencies • Quality-price relationship • Conspicuous necessities. • Ignorance • Change in fashion, habits, attitudes, etc.. • Importance: • Price determination. • To Finance Minister • To farmers • In the field of Planning.

  18. Price Elasticity • Price Elasticity • Elastic Demand or more than 1 – When quantity demanded responds greatly to price changes • Inelastic Demand or less than 1 – When quantity demanded responds little to price changes. • Unitary Elastic – When quantity demanded responds equally to the price changes. • Perfectly inelastic or 0 elastic demand • Perfectly elastic or infinite elastic demand • Economic factors determine the size of price elasticity for individual goods. Elasticity tends to be higher when the goods are luxuries, when substitutes are available and when consumer have more time to adjust their behavior.

  19. Calculating Price Elasticity • PED = % Change in Qty Demanded • % Change in Price • Points to Remember: • We drop the minus sign from the numbers by treating all % changes as positive. That means all elasticity’s are positive, even though prices and quantities move in the opposite direction because of the law of downward sloping demand. • Definition of elasticity uses percentage changes in price and demand rather than actual changes. That means that a change in the units of measurement does not affect the elasticity. So whether we measure price in Rupees or paisa, the price elasticity stays the same.

  20. Some business applications of Price Elasticity • Price discrimination • Public utility pricing (electricity, railway) • Joint supply (wool and mutton) • Super markets • Use of machines (lower cost of production for elastic) • Factor pricing (workers producing inelastic demand products) • International trade (devalue when exports are price-elastic) • Shifting of tax burden (shift commodity tax when demand is inelastic) • Taxation policy

  21. Elasticity & Revenue: • When demand is price inelastic, marginal revenue is negative and a price decrease reduces total revenue. • When demand is price elastic, marginal revenue is positive and a price decrease increases total revenue. • In the borderline case of unit elastic demand, marginal revenue is 0 and a price change leads to no change in the total revenue. • B. Income Elasticity of Demand: Is the degree of responsiveness of quantity demanded of a good to a small change in the income of the consumer. • If the proportion of income spent on a good remains the same as income increases, then income elasticity for the good is equal to one. • If the proportion spent on a good increases, then the income elasticity for the good is greater than one. • If the proportion decreases as income rises, then income elasticity for the good is less than one.

  22. Income elasticity • Types: • Zero • Negative • Positive (i) low (ii) unitary (iii) high • Empirical evidence suggests that income elasticity falls as income rises. • Income elasticity and business decisions • If eiis >0 but <1, sales will increase but slower than the general economic growth; • If ei is >1, sales will increase more rapidly than general economic growth • Corollary: in a growing economy while farmers suffer as their products have low income elasticity, industrialists gain as their products have high income elasticity.

  23. Cross Elasticity: A change in the demand for one good in response to a change in the price of another good represents cross elasticity of demand of the former good for the latter good. • If two goods are perfect substitutes for each other cross elasticity is infinite and if the two goods are totally unrelated, cross elasticity between them is zero. • Goods between which cross elasticity is positive can be called Substitutes, the good between which the cross elasticity is negative are not always complementary as this is found when the income effect on the price change is very strong.

  24. Degrees of Elasticity of Demand • Perfectly Elastic • Perfectly Inelastic • Unitary Elastic • Relatively more elastic • Relatively less elastic

  25. Y p O X d d1 Perfectly Elastic Ed = ∞

  26. Y p1 Ed = 0 p O X d 2. Perfectly Inelastic

  27. Y p1 Ed = 1 p O X d d1 3. Unitary Elastic

  28. Y p1 Ed > 1 p O X d d1 4. Relatively more Elastic

  29. Y p1 Ed < 1 p O X d d1 5. Relatively less Elastic

  30. Figure 7.3 Elastic and inelastic demandDemand curves differ in their relative elasticity. Curve D1 is more elastic than curve D2, inthe sense that consumers on curve D1 are more responsive to a given price change (P2 toP1) than are consumers on curve D2.

  31. Changes in the elasticity coefficientThe elasticity coefficient decreases as a firm moves down the demand curve. The upper half of a linear demand curve is elastic, meaning that the elasticity coefficient is greater than one. The lower half is inelastic, meaning that the elasticity coefficient is less than one. This means that the middle of the linear demand curve has an elasticity coefficient equal to one.

  32. Network effects and demandAs the price falls from P3 to P2, the quantity demanded in the short run rises from Q1 to Q2.However, sales build on sales, causing the demand in the future to expand outward to, say,D2. The lower the price in the current time period, the greater the expansion of demand inthe future. The more the demand expands over time in response to greater sales in thecurrent time period, the more elastic is the long-run demand.

  33. Methods of measurement of Elasticity • Percentage or Proportionate Method • = Percentage change in demand or; • Percentage change in price • = Proportionate change in demand • Proportionate change in price • 2. Total Outlay (Expenditure) Methods • TO=TQ * P ; where, • TO=total outlay; TQ=total quantity; P=price of the commodity • 3. Geometric (Point) method – at any given point on the curve • = lower segment of demand curve • upper segment of demand curve

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