Substitution Effect,
Income Effect
&
Price Effect
Substitution Effect (S.E.)
• Definition: It refers to the change in quantity demanded
for a good caused by a change in relative price, holding
real income constant.
Substitution Effect (S.E.)
• Definition: It refers to the change in quantity demanded
for a good caused by a change in relative price, holding
real income constant.
Qy

Px
Qx

0

Qx0

Qx1

Qx
Substitution Effect (S.E.)
• Definition: It refers to the change in quantity demanded
for a good caused by a change in relative price, holding
real income constant.
Qy

Px
Qx

0

Qx1

Qx0

Qx
Substitution Effect (S.E.)
Px

Qx

Px

Qx
Income Effect (I.E.)
• Definition: It refers to the change in quantity demanded
for a good caused by a change in real income, holding
relative price constant.
Income Effect (I.E.)
• Definition: It refers to the change in quantity demanded
for a good caused by a change in real income, holding
relative price constant.
Qy

I
Qx

0

Qx0 Qx1

Qx
Income Effect (I.E.)
• Definition: It refers to the change in quantity demanded
for a good caused by a change in real income, holding
relative price constant.
Qy

I
Qx

0

Qx1 Qx0

Qx
Income Effect (I.E.)
I

Qx

I

Qx
Normal Goods !!
Income Effect (I.E.)
I

Qx

I

Qx
Normal Goods !!
Income Effect (I.E.)
Inferior
Good

Normal Good

Qy

I

Qy

Qx

I

0

0
Qx0 Qx1

Qx

Qx1 Qx0

Qx

Qx
Income Effect (I.E.)
Inferior
Good

Normal Good

Qy

I

Qy

Qx

I

0

0
Qx1 Qx0

Qx

Qx0 Qx1

Qx

Qx
Income Effect (I.E.)

• Inferior Good:

I

Qx

I

• Normal Good:

Qx

I

Qx

I

Qx
Price Effect (P.E.)
• Definition: It refers to the change in quantity demanded
for a good caused by a change in relative price.
Price Effect (P.E.)
• Definition: It refers to the change in quantity demanded
for a good caused by a change in relative price.
Qy

Px
Qx

0

Qx0

Qx1

Qx
Price Effect (P.E.)
• Definition: It refers to the change in quantity demanded
for a good caused by a change in relative price.
Qy

Px
Qx

0

Qx1

Qx0

Qx
Relative price changes
(S.E.)
When price changes
(P.E.)
Real income changes
(I.E.)
P.E. = S.E. + I.E.
Relative price changes
(S.E.)
When price changes
(P.E.)
Real income changes
(I.E.)
P.E. = S.E. + I.E.
S.E.
P.E.
I.E.

-ve

Px ↓
Px ↑

Qx ↑
Qx ↓
I↓
I↑

Qx ↓
Qx ↑

inferior gd I ↓
-ve
I↑

Qx ↑
Qx ↓

normal gd
+ve
Case 1

Qx ↑

S.E. : Px ↓ Qx ↑
normal gd : I ↑ Qx ↑
+ve

P.E.

Assume Px ↓

I.E.
inferior gd : I ↑ Qx ↓
-ve
S.E. : Px ↓ Qx ↑
P.E.

normal gd : I ↑ Qx ↑
+ve

Px ↓

I.E.
inferior gd : I ↑ Qx ↓
-ve

Qx ?
S.E.

Px ↓ Qx ↑

S.E. > I.E.

I.E.

S.E. < I.E.

inferior gd
I ↑ Qx ↓

Qx ↑

Qx ↓

Case 2

Case 3
Summary
-ve S.E. & +ve I.E.
Qx ↑ & Qx ↑

Px ↓

-ve S.E. > -ve I.E.
Qx ↑ > Qx ↓

-ve S.E. < -ve I.E.
Qx ↑ < Qx ↓

Case 1

Qx ↑

normal gd

Case 2
Qx ↑

inferior gd
non-giffen case

Qx ↓

Case 3
inferior gd
giffen case
Graphically
Case 1 Normal good
Qy

S.E. Qx ↑
-ve

Px ↓
I.E. Qx ↑
+ve
0

Qx0

Qx0’ Qx1

Qx

Qx ↑
Graphically
Case 1 Normal good
Qy

S.E. Qx ↑
-ve

Px ↓
I.E. Qx ↑
+ve
0

Qx0 Qx0’

Qx1

Qx

Qx ↑
Graphically
Case 2

Inferior good, non-giffen case

Qy

S.E. Qx ↑

Px ↓

-ve

S.E.>I.E.

I.E. Qx ↓
-ve

0

Qx0 Qx1 Qx0’

Qx

Qx ↑
Graphically
Case 2

Inferior good, non-giffen case

Qy

S.E. Qx ↑

Px ↓

-ve

S.E.>I.E.

I.E. Qx ↓
-ve

0

Qx0 Qx1 Qx0’

Qx

Qx ↑
Graphically
Case 3

Inferior good, giffen case

Qy

S.E. Qx ↑
-ve

Px ↓

S.E.<I.E.

I.E. Qx ↓
-ve

0

Qx1 Qx0

Qx0’

Qx

Qx ↓
Graphically
Case 3

Inferior good, giffen case

Qy

S.E. Qx ↑
-ve

Px ↓

S.E.<I.E.

I.E. Qx ↓
-ve

0

Qx1 Qx0

Qx0’

Qx

Qx ↓

Effects ppt