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Demand - Microeconomics

  1. A luxury brand of handbag dramatically increases its price. The company observes that for its wealthiest clientele, the quantity demanded does not fall, but actually increases slightly. This behavior is most consistent with the concept of:
    Answer: A Veblen good, where demand is driven by conspicuous consumption and status. This question tests your understanding of unusual demand patterns that violate the typical law of demand. When you encounter scenarios where higher prices lead to increased demand, you need to identify which economic concept explains this counterintuitive behavior. The correct answer is D because Veblen goods are luxury items where higher prices actually increase demand among wealthy consumers. These goods derive value from their exclusivity and ability to signal status. When the handbag's price increases, it becomes more desirable to wealthy clientele precisely because it's more expensive and exclusive. The higher price enhances the product's status symbol value, making it more attractive for conspicuous consumption. A is incorrect because Giffen goods involve necessities where consumers buy more when prices rise due to income constraints forcing substitution away from other goods. This applies to basic necessities, not luxury handbags for wealthy consumers. B is wrong because perfectly inelastic demand means quantity stays exactly the same regardless of price changes. Here, quantity demanded actually increases with the price rise, indicating responsiveness to price. C is incorrect because inferior goods see decreased demand when consumer income rises. The scenario describes wealthy consumers increasing their purchases, which is the opposite pattern of an inferior good. Study tip: Remember that Veblen goods are luxury items where the high price itself creates value through exclusivity and status signaling. This is distinct from Giffen goods (poor-quality necessities) and applies specifically to conspicuous consumption among wealthy consumers.
  2. A firm notices that when they reduce the price of their premium coffee from $6 to $5, sales increase from 100 to 140 cups per day. Simultaneously, sales of their regular coffee (priced at $3) decrease from 200 to 180 cups per day. What is the cross-price elasticity of demand between regular coffee and premium coffee?
    Answer: +0.6 Cross-price elasticity = (% change in quantity of regular coffee) / (% change in price of premium coffee). Regular coffee quantity changes from 200 to 180, a decrease of 10%. Premium coffee price changes from $6 to $5, a decrease of 16.67%. Cross-price elasticity = (-10%) / (-16.67%) = +0.6. The positive sign indicates these are substitute goods. Choice A has the wrong sign. Choice B incorrectly calculates the percentage changes. Choice D uses an incorrect denominator calculation.
  3. A new government policy provides a significant per-unit subsidy to consumers who purchase electric vehicles (EVs). Assuming that home charging stations are a strong complement to EVs, what is the most likely initial effect of the subsidy on the demand for home charging stations?
    Answer: The demand curve for home charging stations will shift to the right. The subsidy effectively lowers the price that consumers pay for EVs. According to the law of demand, a lower price for EVs will lead to an increase in the quantity of EVs demanded. Since home charging stations are a complement to EVs, an increase in the consumption of EVs will lead to an increase in the demand for the complementary good. This is represented by a rightward shift of the demand curve for home charging stations.
  4. In a market with two consumers, Alice and Bob, the individual demand functions are given by QA=20−2PQ_A = 20 - 2P and QB=30−PQ_B = 30 - P. What is the total quantity demanded in the market at a price of $8?
    Answer: 26 To find the market demand, we horizontally sum the individual quantities demanded at a given price. First, we must ensure both consumers are in the market at P=$8. Alice's choke price (price at which QA=0Q_A=0) is $10. Bob's choke price is $30. Since $8 is below both choke prices, both will demand a positive quantity. QA=20−2(8)=20−16=4Q_A = 20 - 2(8) = 20 - 16 = 4. QB=30−8=22Q_B = 30 - 8 = 22. The total market quantity demanded is QM=QA+QB=4+22=26Q_M = Q_A + Q_B = 4 + 22 = 26.
  5. The price of wheat, a key input in the production of bread, falls significantly. At the same time, a popular new diet that discourages carbohydrate consumption becomes a national trend. What are the combined effects on the market demand for bread?
    Answer: The demand for bread will decrease due to the new diet trend. This question requires distinguishing between factors that shift demand and factors that shift supply. The change in the price of wheat, an input, affects the supply of bread (it would shift supply to the right), not the demand. The new diet trend directly affects consumers' tastes and preferences, which is a primary determinant of demand. Since the diet discourages bread consumption, it will cause a decrease in the demand for bread, shifting the demand curve to the left. The change in wheat price is irrelevant to the demand curve itself.
  6. The market demand for artisanal coffee is affected by two recent events: a widely-reported medical study suggesting that daily coffee consumption significantly improves long-term health, and a simultaneous increase in the price of premium tea, a popular alternative. What is the expected net effect on the demand curve for artisanal coffee?
    Answer: The demand curve will shift to the right, but the magnitude of the shift is ambiguous. Both events cause the demand for artisanal coffee to increase. The positive health report increases consumer tastes and preferences for coffee, shifting the demand curve to the right. An increase in the price of a substitute good (premium tea) causes consumers to switch to coffee, also shifting the demand curve for coffee to the right. Since both effects push demand in the same direction, the net effect is a definitive shift to the right. The exact magnitude, however, would depend on the relative strength of these two effects, which is not specified.
  7. The demand for lumber is a derived demand. A sharp increase in mortgage interest rates makes it more expensive for individuals to finance home purchases. What is the likely immediate consequence for the demand curve for lumber?
    Answer: It will shift to the left, as the demand for new home construction decreases. Derived demand means that the demand for a good or factor of production (lumber) depends on the demand for another good or service (new homes). Higher mortgage rates increase the cost of buying a new home, which will decrease the demand for new homes. Since lumber is a key input in home construction, the decrease in demand for new homes will lead to a decrease in the demand for lumber. This is represented by a leftward shift of the demand curve for lumber.
  8. Economists observe that during economic recessions, when average household income falls, the demand for instant noodles increases, while the demand for restaurant meals decreases. This observation implies that:
    Answer: Instant noodles are an inferior good and restaurant meals are a normal good. An inferior good is a good for which demand increases as consumer income decreases. A normal good is a good for which demand decreases as consumer income decreases. The stem states that when income falls, demand for instant noodles increases, making them an inferior good. Conversely, demand for restaurant meals decreases as income falls, making them a normal good. While they are substitutes, this is not the primary implication related to the income change.
  9. A consumer allocates their budget between two goods: books and movies. When the price of books increases by 15%, the consumer's expenditure on books increases by 8%, while their expenditure on movies decreases by 12%. What can be concluded about the consumer's demand behavior?
    Answer: Books have inelastic demand with elasticity -0.47, and books and movies are substitutes When expenditure on books increases by 8% despite a 15% price increase, quantity must have decreased. Using expenditure = price × quantity: if expenditure rose 8% and price rose 15%, then quantity fell by approximately 6.1% [(1.08/1.15) - 1 = -0.061]. Price elasticity = -6.1%/15% ≈ -0.47, which is inelastic. The decrease in movie expenditure when book prices rise suggests substitution between the goods. Choice A uses incorrect elasticity calculation. Choices C and D incorrectly conclude demand is elastic.
  10. A monopolist faces the demand function P=24−2QP = 24 - 2Q and currently charges $16. If they want to increase total revenue, and they know that demand follows the law of demand, what pricing strategy should they pursue and why?
    Answer: Decrease price because demand is elastic in the current price range, so lower prices increase revenue At P = $16: Q = (24-16)/2 = 4. Current revenue = $64. The midpoint of the linear demand curve occurs at P = $12, Q = 6, where elasticity = -1. Since the firm is currently charging above the midpoint price, demand is elastic (|E| > 1). With elastic demand, reducing price increases total revenue. Choice A incorrectly identifies demand as inelastic. Choice C incorrectly states they're at the revenue maximum. Choice D correctly suggests decreasing price but gives an incorrect reason about marginal revenue.
  11. A technological innovation significantly lowers the production cost of smartphones, leading to a fall in their market price. Which of the following statements best describes the resulting change in consumer surplus in the smartphone market?
    Answer: Consumer surplus will increase due to a lower price for existing buyers and the entry of new buyers. Consumer surplus is the area between the demand curve and the price line. When the market price falls, this area increases for two reasons. First, existing consumers who would have bought the product at the higher price now get more surplus on each unit because they pay less. Second, the lower price induces new consumers (who were not willing to buy at the old, higher price) to enter the market, and they receive some consumer surplus on their purchases. Both effects lead to an unambiguous increase in total consumer surplus.
  12. A consumer's demand for good X increases by 20% when their income rises from $40,000 to $50,000, while the price of good X remains constant at $10 per unit. If the consumer's demand function can be approximated as linear in income over this range, what is the income elasticity of demand for good X?
    Answer: 0.8 Income elasticity of demand = (% change in quantity demanded) / (% change in income). The quantity demanded increases by 20%, and income increases from $40,000 to $50,000, which is a 25% increase [($50,000 - $40,000)/$40,000 = 0.25]. Therefore, income elasticity = 20%/25% = 0.8. Choice B incorrectly uses 20% as both numerator and denominator. Choice C incorrectly inverts the calculation (25%/20%). Choice D incorrectly calculates the income change as 50% instead of 25%.
  13. A consumer's demand for luxury watches is described by the function Q=I1.5P0.8Q = \frac{I^{1.5}}{P^{0.8}} where I is income and P is price. If the consumer's income increases by 20% while price remains constant, what type of good is this and what is the income elasticity of demand?
    Answer: Normal good with income elasticity of 1.5, indicating it is a luxury good When you encounter a demand function with income and price variables, you're being tested on income elasticity of demand—a measure of how responsive quantity demanded is to changes in income. The key is to identify the exponent on income (I) in the demand function. In the given function Q=I1.5P0.8Q = \frac{I^{1.5}}{P^{0.8}}, the exponent on income is 1.5, which directly gives you the income elasticity of demand. When income increases by any percentage, quantity demanded will increase by 1.5 times that percentage. Since the elasticity is positive, this confirms it's a normal good (demand increases with income). Moreover, since the elasticity exceeds 1.0, it's specifically a luxury good—consumers will disproportionately increase their consumption as their income rises. Choice A incorrectly states the income elasticity as 1.2, possibly confusing the 20% income increase with the elasticity coefficient. Choice B uses 0.8, which is actually the price elasticity (the exponent on P), not the income elasticity—this represents a common trap of mixing up the exponents. Choice C incorrectly identifies this as an inferior good with negative elasticity; inferior goods would have negative exponents on income, but here the exponent is clearly positive. Remember this pattern: in multiplicative demand functions like this one, the exponent on income IS the income elasticity of demand. Positive values indicate normal goods, with values above 1.0 representing luxuries and values below 1.0 representing necessities.
  14. A grocery store manager observes that when the price of peanut butter is lowered, the total sales of jelly increase, and the total sales of almond butter decrease. This suggests that in this market:
    Answer: jelly is a complement to peanut butter, and almond butter is a substitute. Cross-price effects determine whether goods are substitutes or complements. When the price of peanut butter falls, quantity demanded for it rises. If jelly sales increase as a result, it means people are consuming more peanut butter and jelly together; they are complements. If almond butter sales decrease when the price of peanut butter falls, it means consumers are switching from almond butter to the now-cheaper peanut butter; they are substitutes. Therefore, jelly is a complement and almond butter is a substitute.
  15. For a particular social media platform, its value to an individual user increases significantly as the total number of users on the platform grows. If a large number of new users are expected to join the platform next month, how will this expectation affect the demand curve for access to the platform today?
    Answer: It will shift today's demand curve to the right, as the anticipated future value is capitalized into current demand. This scenario describes a network effect, where the value of a product depends on the number of users. The expectation of future growth increases the platform's anticipated value. Rational consumers will factor this expected increase in value into their decision to join today. This increased willingness to pay at every quantity level shifts the entire demand curve to the right. This is a form of the 'expectations' determinant of demand.
  16. An economist observes that when gasoline prices rose 25% last year, a consumer's gasoline purchases fell 15%, while their public transit usage increased 40%. The consumer's income remained constant. What is the cross-price elasticity of demand between gasoline and public transit?
    Answer: +1.6, indicating these are substitute goods with strong responsiveness Cross-price elasticity of demand measures how responsive the quantity demanded of one good is to a change in the price of another good. When you see a question involving two related products and a price change in one affecting demand for the other, you're dealing with this concept. To calculate cross-price elasticity, use the formula: % change in quantity demanded of good X% change in price of good Y\frac{\% \text{ change in quantity demanded of good X}}{\% \text{ change in price of good Y}} Here, gasoline price rose 25% and public transit usage increased 40%, so: +40%+25%=+1.6\frac{+40\%}{+25\%} = +1.6 The positive sign tells you these are substitute goods—when gasoline becomes more expensive, people switch to public transit. The magnitude of 1.6 indicates strong responsiveness since it's greater than 1. Option A is wrong because it uses -0.625, which would indicate complementary goods (negative sign) and incorrectly suggests people use less public transit when gas prices rise. Option B has the wrong magnitude—it appears someone incorrectly used gasoline's quantity change (-15%) in the numerator instead of public transit's change (+40%). Option C uses -1.6, which has the correct magnitude but wrong sign, again incorrectly suggesting these are complements rather than substitutes. Remember: positive cross-price elasticity means substitutes (price of one up, demand for other up), while negative means complements. Values greater than 1 in absolute terms indicate strong responsiveness, while values less than 1 indicate weak responsiveness.
  17. A severe potato famine in a poor country leads to a sharp increase in the price of potatoes, which are the main source of calories for the population. An economist observes that despite the price increase, the consumption of potatoes by low-income households has actually risen. This paradoxical situation suggests that for these households, potatoes are:
    Answer: A Giffen good. This scenario describes a Giffen good, which is a rare type of inferior good that violates the law of demand. When the price of a Giffen good rises, the quantity demanded also rises. This occurs because the good is a dietary staple for a very poor population. The price increase has a large negative income effect, making consumers so much poorer that they cut back on more expensive 'luxury' foods (like meat) and buy more of the staple good (potatoes) to get enough calories to survive. The strong income effect outweighs the substitution effect.
  18. The estimated demand function for product X is Qdx=1,500−3Px+0.05I−2.5Py+4PzQ_{dx} = 1,500 - 3P_x + 0.05I - 2.5P_y + 4P_z, where PxP_x is the price of X, II is consumer income, PyP_y is the price of good Y, and PzP_z is the price of good Z. Based on this function, which of the following statements is correct?
    Answer: Good Y is a complement to good X, and good Z is a substitute for good X. We analyze the signs of the coefficients. The coefficient on income (I) is +0.05, which is positive, indicating that as income increases, the quantity demanded of X increases. Therefore, X is a normal good. The coefficient on the price of good Y (PyP_y) is -2.5, which is negative. This means that as the price of Y increases, the quantity demanded of X decreases. This relationship defines complementary goods. The coefficient on the price of good Z (PzP_z) is +4, which is positive. This means that as the price of Z increases, the quantity demanded of X increases. This relationship defines substitute goods. Therefore, Y is a complement and Z is a substitute.
  19. Which of the following scenarios describes a change in quantity demanded rather than a change in demand?
    Answer: A university lowers its tuition fee, and the number of student applications increases. When you encounter questions about demand changes, you need to distinguish between a "change in demand" (the entire demand curve shifts) versus a "change in quantity demanded" (movement along the same demand curve due to price changes). Option D is correct because it describes a price change leading to more applications. When the university lowers tuition fees, students move along the existing demand curve to a point where they're willing to "purchase" more education at the lower price. This is a change in quantity demanded—the relationship between price and quantity hasn't fundamentally changed, just the price point. Let's examine why the other options represent demand shifts: Option A describes a celebrity endorsement, which is a change in consumer preferences—a non-price factor that shifts the entire demand curve rightward. Option B shows a complementary goods relationship where cheaper computer hardware increases demand for software, shifting software's demand curve due to the price change of a related good. Option C illustrates how rising incomes affect luxury car sales, representing an income effect that shifts the demand curve for normal goods. The key distinction is whether price or non-price factors cause the change. Price changes create movements along the demand curve (quantity demanded changes), while non-price factors like preferences, income, or prices of related goods shift the entire curve (demand changes). Remember this pattern: if the question mentions the product's own price changing, look for quantity demanded changes. If it mentions income, preferences, related goods, or expectations changing, think demand shifts.
  20. A market's demand curve is given by the equation Qd=200−5PQ_d = 200 - 5P. If the price falls from $30 to $20, the resulting increase in the quantity demanded is attributable to:
    Answer: both the substitution effect and the income effect. A change in the price of a good always triggers both an income effect and a substitution effect (unless one is zero, which is rare). The substitution effect is the change in consumption due to the good becoming relatively cheaper than other goods. The income effect is the change in consumption due to the change in the consumer's real purchasing power. For a normal good, both effects work in the same direction for a price decrease, leading to an increase in quantity demanded. The movement along the demand curve from P=$30 (Q=50) to P=$20 (Q=100) is the total effect, which is the sum of these two underlying effects. An outward shift would be a change in demand, not quantity demanded.

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