When we observe an increase in both price and quantity, we...

When we observe an increase in both price and quantity, we know that the demand curve must have shifted rightward. However, we cannot rule a shift in the supply curve as well. Prove this by drawing a supply-and-demand diagram for each of the following cases: a. Demand curve shifts rightward, supply curve shifts leftward, equilibrium price and quantity both rise. b. Demand and supply curves both shift rightward, equilibrium price and quantity both rise. c. Evaluate the following statement: "During the oil price spike from 2007 to mid- 2008 , we know the supply curve could not have shifted leftward, because quantity supplied rose." True or False? Explain.

When we observe an increase in both price and quantity, we know that the demand curve must have shifted rightward. However, we cannot rule a shift in the supply curve as well. Prove this by drawing a supply-and-demand diagram for each of the following cases:
a. Demand curve shifts rightward, supply curve shifts leftward, equilibrium price and quantity both rise.
b. Demand and supply curves both shift rightward, equilibrium price and quantity both rise.
c. Evaluate the following statement: "During the oil price spike from 2007 to mid- 2008 , we know the supply curve could not have shifted leftward, because quantity supplied rose." True or False? Explain.

Key Concepts

Market Equilibrium

Market equilibrium is the point where the supply and demand curves intersect, representing the price at which the quantity supplied equals the quantity demanded. Changes in the position of either the supply or demand curve will shift the equilibrium, resulting in a new balance of price and quantity in the market.

Demand Curve Shift

A demand curve shift occurs when a non-price determinant of demand changes, resulting in the entire demand curve moving either to the right (increase in demand) or to the left (decrease in demand). This change implies that at every price level, consumers are willing to purchase a different quantity than before, which alters the equilibrium outcome in the market.

Supply Curve Shift

A supply curve shift happens when there is a change in non-price factors affecting supply—such as production technology, input prices, or government policies—causing the entire curve to move. A rightward shift indicates an increase in supply at every price, whereas a leftward shift indicates a decrease, thereby affecting the market equilibrium in terms of both price and quantity.

Simultaneous Shifts Analysis

Simultaneous shifts in both the demand and supply curves require a comparative statics approach to analyze the overall impact on equilibrium. In these cases, the direction and magnitude of each shift determine the net effect on equilibrium price and quantity. For instance, an increase in demand coupled with a leftward shift in supply might lead to a higher price and potentially a higher or lower quantity, depending on the relative shifts, illustrating the complexity of interactions in the market.

Transcript

00:01 Simultaneous shifts in supply and demand can have unambiguous effects on price and quantity if, and only if, we know which shift had a more significant effect.

00:14 So let's look at three different examples of this.

00:17 In the first example, we're told that the demand curve shifted right, the supply curve shifted left, but in the end, the equilibrium price and quantity both rose.

00:27 So let's draw a supply curve and a demand curve.

00:33 Don't forget to label your axes.

00:36 And in this example, let's say that demand shifted to the right by a lot.

00:41 There was a very significant shift in demand.

00:46 But supply shifted to the left, but only by a little bit.

00:53 Well, if these two effects happen in tandem, the demand shift would imply that there is an increase in price and an increase in quantity.

01:03 The supply shift would imply an increase in price, but a decrease in quantity.

01:09 But since we know that the demand shift was larger, it will more or less overtake the effect of the supply shift.

01:15 So overall, price will increase and quantity will increase.

01:22 Even though the supply shift would tend to decrease quantity, the demand shift just had a much larger effect.

01:29 In our second example, we're told that the demand and supply curves both shift to the right...

Please give Ace some feedback