Business Economics · Theory of Demand and Supply

Movement vs Shift in Demand Curve (CA Foundation Business Economics)

Updated 1 October 2026 · Fact-checked

A movement along the demand curve happens only when the good's own price changes: extension if price falls, contraction if price rises. A shift happens when any other factor changes, such as income or tastes: rightward is an increase, leftward is a decrease. Ask first: did own price change?

Understand Movement vs Shift in Demand Curve

A demand curve shows the quantity of a good consumers will buy at each price, keeping all other factors constant (ceteris paribus). This is why one single question decides every problem in this topic: what changed?

If the price of the good itself changes, you move to another point on the same curve. A fall in price raises quantity demanded. This is called extension of demand. A rise in price lowers quantity demanded. This is called contraction of demand. The curve does not move.

If any other factor changes, the whole curve moves to a new position. These factors include income, tastes and preferences, prices of related goods (substitutes and complements), population and expectations about future prices. More demand at every price means a shift to the right: increase in demand. Less demand at every price means a shift to the left: decrease in demand.

The law of demand says that, other things equal, price and quantity demanded move in opposite directions. A few cases appear to break it. A Giffen good is a strongly inferior good with no close substitute that takes a large share of a poor household's budget. When its price rises, the household cannot afford better food and buys more of it. A Veblen good (conspicuous consumption) is bought for status, so a higher price makes it more desirable. Expectations of further price rises can also make people buy more at a higher price. Necessities and ignorance are sometimes listed too.

In the exam, the wording gives it away. Phrases like 'due to a fall in its price' signal movement. Phrases like 'rise in income' or 'change in fashion' signal a shift.

Key formulas to remember

Movement along the curve: Own price ↓ → extension of demand; Own price ↑ → contraction of demand; Same demand curve. Only the own price of the good changes.
Shift of the curve: Rightward shift = increase in demand; Leftward shift = decrease in demand; Caused by a change in any factor other than own price.
Normal good and income: Income ↑ → demand ↑ (right shift); Income ↓ → demand ↓ (left shift); For an inferior good the direction is reversed.
Related goods: Substitute price ↑ → demand for this good ↑; Complement price ↑ → demand for this good ↓; Applies to the price of the other good, not this good.
Exceptions to the law of demand: Giffen goods, Veblen goods, expectation of price rise; In these cases the demand curve may slope upward.

How to solve Movement vs Shift in Demand Curve questions

Use this method for any question on movement or shift. It takes under a minute.

1Identify the good whose demand is being discussed.
2Find what changed in the question. Is it the price of that same good, or something else?
3If it is the good's own price, it is a movement along the curve. Fall means extension, rise means contraction.
4If it is any other factor, it is a shift. Decide whether that factor raises or lowers demand at every price.
5Check for traps: inferior good, complement versus substitute, and whether the question says 'quantity demanded' or 'demand'.
6Name the result exactly: extension, contraction, increase or decrease.
7For exception questions, match the description (poor household staple, status good, expected price rise) to Giffen, Veblen or expectations.

Quickest way: One-question filter: did own price change?

When to use it: Use in every MCQ on this topic, especially when options are close and negative marking applies.

Underline the cause in the question.
Own price = movement. Anything else = shift.
Remember the words: 'quantity demanded' goes with movement; 'demand' goes with shift.
Eliminate options that use the wrong pair of terms. Extension and contraction never go with a shift.
For related goods, ask: does the other good's price change make this good more wanted? Substitute yes when its price rises, complement no.
Skip only if the good is unclear. Otherwise this is a fast, safe question.

Common mistakes in Movement vs Shift in Demand Curve

Calling a price fall an 'increase in demand'.
In everyday speech, demand and quantity demanded sound the same.
Fix: A change in own price gives extension or contraction only. Reserve 'increase' and 'decrease' for shifts.
Shifting the curve when a good's own price changes.
Students think a bigger quantity means a new curve.
Fix: The curve already shows every price-quantity pair. Move along it.
Treating a complement's price rise as raising demand.
Confusing substitutes with complements.
Fix: Complements are used together, so a price rise in one lowers demand for the other. Substitutes work the opposite way.
Applying 'income up, demand up' to inferior goods.
Memorising the rule for normal goods only.
Fix: For an inferior good, higher income shifts demand left as people switch to better goods.
Saying Giffen and Veblen goods are the same thing.
Both show a price rise with higher quantity bought.
Fix: Giffen: poor household, inferior staple, income effect dominates. Veblen: status goods bought because the price is high.
Assuming the law of demand fails for any price rise with higher demand.
Ignoring that another factor (such as income) may have shifted the curve at the same time.
Fix: First check if something else changed. A true exception needs a reason tied to the good itself.

Worked examples

Example 1

The price of tea falls and consumers buy more tea, other things unchanged. This is: (a) Increase in demand (b) Extension of demand (c) Decrease in demand (d) Contraction of demand

Show the solution

The cause is a change in the own price of tea.
So this is a movement along the same demand curve.
Price fell and quantity rose, which is extension.
Options (a) and (c) describe shifts, so they are out. Option (d) needs a price rise.

Answer: (b) Extension of demand

Example 2

Coffee and tea are substitutes. The price of tea rises. What happens to the demand curve for coffee? (a) Movement downward along the curve (b) Shift to the right (c) Shift to the left (d) No change

Show the solution

The price that changed is tea, not coffee, so coffee's own price is unchanged.
That means a shift, not a movement. Option (a) is out.
Tea is a substitute, so people switch to coffee.
Demand for coffee rises at every price, so the curve shifts right.

Answer: (b) Shift to the right

Example 3

A poor household buys more of a staple inferior grain when its price rises, as it cannot afford better food. This good is best described as: (a) Veblen good (b) Normal good (c) Giffen good (d) Complementary good

Show the solution

The demand rises with price, so it is an exception to the law of demand.
The household is poor and the good is an inferior staple.
Higher price cuts real income, so people drop better foods and buy more of the staple.
A Veblen good is bought for status, which does not fit.

Answer: (c) Giffen good

Exam tips

Read the cause first, then the options. One look at the cause decides movement or shift.
Watch the words 'quantity demanded' versus 'demand'. Examiners use them deliberately.
For related goods, write S or C next to the other good and apply the rule before choosing.
Learn the Giffen versus Veblen difference in one line each. Direct questions on this are common.
With 0.25 negative marking, attempt these questions. They are easy marks once the filter is clear.

Practice questions from Theory of Demand and Supply

Movement vs Shift in Demand Curve: frequently asked questions

What is the difference between a movement along and a shift of the demand curve?

A movement happens when the good's own price changes, and you stay on the same curve. A shift happens when any other factor changes, such as income or tastes, and the whole curve moves left or right.

What is the difference between extension of demand and increase in demand?

Extension is a rise in quantity demanded because the price fell, shown by a move down the same curve. Increase in demand means more is demanded at every price, shown by a rightward shift of the curve.

What are the exceptions to the law of demand?

The main ones are Giffen goods, Veblen goods (status goods) and cases where people expect prices to rise further. In these cases, a higher price may lead to higher quantity demanded.

Why do Giffen goods break the law of demand?

A Giffen good is a strongly inferior staple that takes a large share of a poor household's budget. When its price rises, the household has less real income and cuts better foods, so it buys more of the Giffen good.