Explain through a diagram the effect of a rightward shift of both the demand and supply curves on equilibrium

Exercises · Q15

Q. Explain through a diagram the effect of a rightward shift of both the demand and supply curves on equilibrium price and quantity.

Yanam CbseNCERTSubjective· 3mImportance★★★★★

59% · 17/29 Questions

🔒 Locked · start free trial →

You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.

Start your 14-day free trial to unlock the full solution →

Concept understanding — Supply And Demand Shift

The Everyday Intuition: Why Did My Chai Cost More Last Month?

Think about the chai-wala near your school. One month, a sudden cold wave hits your city. Everyone wants hot chai. The chai-wala can only make so many cups per hour. What happens? He might raise the price from ₹10 to ₹12. You grumble, but you still buy it because you're cold. That's demand shifting — more people wanting chai at every price.

Now imagine a different scenario: a truckers' strike makes milk and sugar expensive to transport. The chai-wala now has to pay more for his ingredients. He can't afford to sell chai at ₹10 anymore. He raises the price to ₹12 just to cover his costs. That's supply shifting — the cost of making chai has changed.

These two stories feel similar — price goes up in both — but the reason is completely different. And that difference is the entire point of this concept.

The Precise Meaning: What "Shift" Actually Means

In economics, demand and supply are not single numbers. They are schedules — a whole list showing how much buyers want (or sellers offer) at every possible price. We draw them as curves on a graph: price on the vertical axis, quantity on the horizontal.

A shift means the entire curve moves — left or right. This is different from a movement along the curve, which happens when only the price changes.

Important

Shift of the curve = a non-price factor changes (income, tastes, input costs, technology).

Movement along the curve = only the price changes.

Demand Shift

The demand curve shows: "At price ₹P, buyers want quantity Q." If something other than price changes how much people want, the whole curve shifts.

Rightward shift (increase in demand): At every price, buyers want more than before.

Leftward shift (decrease in demand): At every price, buyers want less.

What causes a demand shift? NCERT Class 12 (Introductory Microeconomics, Chapter 5) lists these factors:

Change in income: For normal goods, higher income → more demand at every price. For inferior goods (like cheap noodles), higher income → less demand.
Change in tastes/preferences: A health report praising green tea shifts its demand curve right.
Change in price of related goods:
- Substitutes (tea and coffee): If coffee becomes expensive, tea demand shifts right.
- Complements (petrol and cars): If petrol becomes expensive, car demand shifts left.
Expectations about future prices: If you think chai will cost ₹15 next week, you buy more today — demand shifts right now.
Number of buyers: More population → more demand at every price.

Supply Shift

The supply curve shows: "At price ₹P, sellers offer quantity Q." If something other than price changes their willingness or ability to sell, the whole curve shifts.

Rightward shift (increase in supply): At every price, sellers offer more.

Leftward shift (decrease in supply): At every price, sellers offer less.

NCERT lists these causes:

Change in input prices: Cheaper raw materials → supply shifts right. Costlier inputs → supply shifts left.
Change in technology: Better machines → produce more at same cost → supply shifts right.
Change in price of other goods (for multi-product firms): If a farmer can grow wheat or rice, and wheat price rises, they shift land to wheat — rice supply shifts left.
Expectations: If sellers expect higher prices next month, they may hold back stock today — supply shifts left.
Number of sellers: More firms enter the market → supply shifts right.
Taxes and subsidies: A tax on production shifts supply left (costs rise). A subsidy shifts supply right (costs fall).

Why It Matters: The New Equilibrium

The market price is determined where demand and supply curves intersect. That intersection is called equilibrium. When a curve shifts, the equilibrium changes.

Here is what happens in words (and you should draw this):

Case 1: Demand shifts right (increase in demand)

At the old price, there is now excess demand — buyers want more than sellers offer.
Sellers raise price. As price rises, some buyers drop out, and sellers produce more.
New equilibrium: Higher price, higher quantity. …

Start your 14-day free trial to unlock the full solution →

When both the demand and supply curves shift rightward (increase), the equilibrium quantity will always increase, but the effect on equilibrium price is ambiguous and depends on the relative magnitudes of the shifts.

Understanding the impact of simultaneous shifts in demand and supply requires first recalling what equilibrium means and how individual shifts affect it. Market equilibrium occurs at the intersection of the demand and supply curves, where the quantity demanded equals the quantity supplied, determining the equilibrium price ( $P_0$ ) and equilibrium quantity ( $Q_0$ ).

A rightward shift in the demand curve signifies an increase in demand. At any given price, consumers are now willing and able to purchase more of the good. If supply remained constant, this increased demand would lead to a shortage at the original price, pushing the equilibrium price up and the equilibrium quantity up.

Similarly, a rightward shift in the supply curve signifies an increase in supply. At any given price, producers are now willing and able to offer more of the good for sale. If demand remained constant, this increased supply would lead to a surplus at the original price, pushing the equilibrium price down and the equilibrium quantity up.

Now, let's consider the combined effect of both curves shifting rightward simultaneously.

Diagrammatic Explanation

Imagine an initial market equilibrium where the demand curve $D_0$ intersects the supply curve $S_0$ at point $E_0$ , yielding an equilibrium price $P_0$ and equilibrium quantity $Q_0$ .

Effect on Equilibrium Quantity:
- An increase in demand (rightward shift of $D_0$ to $D_1$ ) tends to increase the equilibrium quantity.
- An increase in supply (rightward shift of $S_0$ to $S_1$ ) also tends to increase the equilibrium quantity.
- Since both forces push the quantity in the same direction (upwards), the new equilibrium quantity ( $Q_1$ ) will unambiguously increase compared to the initial quantity ( $Q_0$ ).
Effect on Equilibrium Price:
- An increase in demand (rightward shift of $D_0$ to $D_1$ ) tends to increase the equilibrium price.
- An increase in supply (rightward shift of $S_0$ to $S_1$ ) tends to decrease the equilibrium price.
- Because these two forces push the price in opposite directions, the net effect on the equilibrium price ( $P_1$ ) is ambiguous. It depends on the relative magnitudes of the shifts. We can illustrate three possible scenarios:
- Scenario 1: Demand shift is greater than the supply shift.
  
  If the rightward shift in demand is proportionally larger than the rightward shift in supply, the upward pressure on price from increased demand will outweigh the downward pressure from increased supply. In this case, the new equilibrium price ( $P_1$ ) will be higher than the initial price ( $P_0$ ). The new intersection point $E_1$ will be above and to the right of $E_0$ .
- Scenario 2: Supply shift is greater than the demand shift. …

Start your 14-day free trial to unlock the full solution →

←Previous questionQ14 — Compare the effect of shift in demand curve on the equilibrium when th…→Next questionQ16 — How are the equilibrium price and quantity affected when (a) both dema…

Q.Explain through a diagram the effect of a rightward shift of both the demand and supply curves on equilibrium price and quantity.

🎓Unlock everything free for 14 days

Unlock everything free for 14 days