AS Economics 9708 Microeconomics Crash Course Class 3 (PED and Intro to YED)

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AS Economics 9708 Microeconomics Crash Course Class 3 (PED and Intro to YED)

**Channel:** Daniyal Aslam

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1. Summary

This video, the third in a crash course series on AS Economics Microeconomics by Daniyal Aslam, focuses on two key concepts: Price Elasticity of Demand (PED) and an introduction to Income Elasticity of Demand (YED). The session thoroughly explains the definition, calculation, interpretation, and factors influencing PED, providing practical examples to solidify understanding. It then transitions to introducing YED, defining it, explaining its formula, and differentiating between normal and inferior goods based on YED values. The video aims to equip students with a solid understanding of these elasticity concepts for their AS Economics exams.

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2. Key Takeaways

* **Price Elasticity of Demand (PED)** measures the responsiveness of quantity demanded to a change in price.

* **Formula for PED:** PED = (% Change in Quantity Demanded) / (% Change in Price)

* **Interpreting PED values:**

* |PED| > 1: Elastic demand (quantity demanded changes proportionally more than price).

* |PED| < 1: Inelastic demand (quantity demanded changes proportionally less than price).

* |PED| = 1: Unit elastic demand (quantity demanded changes by the same proportion as price).

* PED = 0: Perfectly inelastic demand (quantity demanded does not change with price).

* |PED| = ∞: Perfectly elastic demand (any price increase leads to zero demand).

* **Factors affecting PED:** Availability of substitutes, necessity vs. luxury, proportion of income spent, time period, and definition of the market.

* **Relationship between PED and Total Revenue (TR):**

* Elastic demand: Price increase -> TR decreases; Price decrease -> TR increases.

* Inelastic demand: Price increase -> TR increases; Price decrease -> TR decreases.

* Unit elastic demand: Price change -> TR remains unchanged.

* **Income Elasticity of Demand (YED)** measures the responsiveness of quantity demanded to a change in income.

* **Formula for YED:** YED = (% Change in Quantity Demanded) / (% Change in Income)

* **Interpreting YED values:**

* YED > 0: Normal good (demand increases as income increases).

* 0 < YED < 1: Necessity (demand increases but less than proportionally to income).

* YED > 1: Luxury (demand increases proportionally more than income).

* YED < 0: Inferior good (demand decreases as income increases).

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3. Detailed Notes

#### I. Price Elasticity of Demand (PED)

**A. Definition:**

* PED quantifies how much the quantity demanded of a good or service changes when its price changes.

* It indicates the degree of responsiveness.

**B. Formula:**

* PED = $\frac{\text{% Change in Quantity Demanded}}{\text{% Change in Price}}$

* **Calculation of Percentage Change:** $\frac{\text{New Value} - \text{Old Value}}{\text{Old Value}} \times 100\%$

**C. Interpretation of PED Values:**

* **Elastic Demand (|PED| > 1):**

* A given percentage change in price leads to a larger percentage change in quantity demanded.

* Consumers are very responsive to price changes.

* Example: Luxury goods, goods with many substitutes.

* **Inelastic Demand (|PED| < 1):**

* A given percentage change in price leads to a smaller percentage change in quantity demanded.

* Consumers are not very responsive to price changes.

* Example: Necessities, goods with few substitutes.

* **Unit Elastic Demand (|PED| = 1):**

* The percentage change in quantity demanded is exactly equal to the percentage change in price.

* **Perfectly Inelastic Demand (PED = 0):**

* Quantity demanded does not change at all, regardless of price changes.

* This is theoretical and rarely occurs in reality.

* Example: Life-saving drugs (in the very short term).

* **Perfectly Elastic Demand (|PED| = ∞):**

* Any increase in price above a certain point causes demand to fall to zero.

* Consumers are infinitely sensitive to price.

* This is also theoretical and often associated with perfectly competitive markets where a single firm faces this.

**D. Factors Affecting PED:**

1. **Availability of Substitutes:**

* More substitutes $\rightarrow$ More elastic demand (consumers can easily switch).

* Fewer substitutes $\rightarrow$ More inelastic demand.

2. **Necessity vs. Luxury:**

* Necessities (e.g., basic food, medicine) $\rightarrow$ More inelastic demand (consumers need them regardless of price).

* Luxuries (e.g., designer clothes, sports cars) $\rightarrow$ More elastic demand (consumers can forgo them if prices rise).

3. **Proportion of Income Spent:**

* Goods that take up a large proportion of income $\rightarrow$ More elastic demand (price changes are more noticeable and impactful).

* Goods that take up a small proportion of income (e.g., salt, matches) $\rightarrow$ More inelastic demand.

4. **Time Period:**

* Longer time period $\rightarrow$ More elastic demand (consumers have more time to find substitutes or adjust consumption habits).

* Shorter time period $\rightarrow$ More inelastic demand.

5. **Definition of the Market:**

* Narrowly defined market (e.g., a specific brand of cola) $\rightarrow$ More elastic demand (many substitutes for similar colas).

* Broadly defined market (e.g., all soft drinks) $\rightarrow$ More inelastic demand (fewer substitutes for soft drinks in general).

**E. PED and Total Revenue (TR):**

* **Total Revenue (TR) = Price (P) x Quantity Demanded (Q)**

* **When Demand is Elastic (|PED| > 1):**

* **Price Increase:** Quantity demanded falls by a greater percentage. $\rightarrow$ TR decreases.

* **Price Decrease:** Quantity demanded rises by a greater percentage. $\rightarrow$ TR increases.

* **When Demand is Inelastic (|PED| < 1):**

* **Price Increase:** Quantity demanded falls by a smaller percentage. $\rightarrow$ TR increases.

* **Price Decrease:** Quantity demanded rises by a smaller percentage. $\rightarrow$ TR decreases.

* **When Demand is Unit Elastic (|PED| = 1):**

* **Price Change:** Percentage change in quantity demanded is equal and opposite. $\rightarrow$ TR remains unchanged.

#### II. Introduction to Income Elasticity of Demand (YED)

**A. Definition:**

* YED measures the responsiveness of the quantity demanded of a good or service to a change in consumers' real income.

**B. Formula:**

* YED = $\frac{\text{% Change in Quantity Demanded}}{\text{% Change in Real Income}}$

**C. Interpretation of YED Values:**

* **Normal Goods (YED > 0):**

* As income increases, the quantity demanded for these goods increases.

* **Sub-categories:**

* **Necessities (0 < YED < 1):** Demand increases, but proportionally less than the increase in income. Consumers can afford more, but their spending on these essentials doesn't skyrocket as their income rises significantly.

* *Examples: Bread, milk, basic clothing.*

* **Luxuries (YED > 1):** Demand increases proportionally more than the increase in income. Consumers with higher incomes tend to spend a larger portion of their additional income on these goods.

* *Examples: Sports cars, designer handbags, foreign holidays.*

* **Inferior Goods (YED < 0):**

* As income increases, the quantity demanded for these goods decreases. Consumers switch to better quality or more preferred alternatives as they become wealthier.

* *Examples: Instant noodles (replaced by fresh pasta), cheap bus travel (replaced by car ownership or faster public transport).*

* **Zero Income Elasticity (YED = 0):**

* Quantity demanded does not change with a change in income. This is theoretical, suggesting the good is not affected by income changes at all.

**D. Importance:**

* Helps businesses predict how changes in the economy (affecting consumer income) will impact demand for their products.

* Crucial for understanding market segmentation and consumer behavior across different income levels.