<p>Utility is constant for all points $(q_B,q_A)$ on an indifference curve. So there is a number $u_1$ such that 
$$
\forall (q_B,q_A) \in IC_1: \ U(q_B,q_A) = u_1.
$$
Similarly there is a number $u_2$, such that
$$
\forall (q_B,q_A) \in IC_2: \ U(q_B,q_A) = u_2.
$$
If $IC_1 \neq IC_2$ then $u_1 \neq u_2$.</p>

CC BY-SA 3.0
2017-01-21T12:46:50.540Z
2017-01-21T12:46:50.540Z
Giskard
<p>If an indifference curve shows quantities where a consumer's utility from consuming two goods are equal, then why are there infinitely many indifference curves? From the diagram, you can have Q1,Q2 on IC1, but then you'd have Q1,Q3 on the other indifference curve, wouldn't that mean the consumer would receive the same utility from consuming Q1 and Q2 as well as if he had consumed Q1 and Q3, i.e. for a given Q1, the consumption of Q2 gives the same amount of utility as Q3? Shouldn't this mean that the indifference curve should be unique?</p>

<p><a href="https://i.sstatic.net/8xUcn.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/8xUcn.jpg" alt="enter image description here"></a></p>

CC BY-SA 3.0
2017-01-21T12:38:57.467Z
"wouldn't that mean the consumer would receive the same utility from consuming Q1 and Q2 as well as if he had consumed Q1 and Q3" Why do  you think this...?
Giskard
CC BY-SA 3.0
2017-01-21T12:42:57.600Z
@denesp If the consumer is receiving 5 utilities from consuming q1 and 5 utilities from consuming q2, and q3 > q2, then how can he be receiving a 5 utilities from q3 as well? But isn't this what IC2 is suggesting, that the total utility of (q1,q2) is the same as (q1,q3)?
tsp216
CC BY-SA 3.0
2017-01-21T12:43:35.380Z
Why do you think he is receiving a 5 utilities from q3 as well? That is not in the definition of IC2 at all.
Giskard
CC BY-SA 3.0
2017-01-21T15:36:27.523Z
you do net get 5 utils from consuming q1! you get, let's say 5 utils from consuming the bundle {Q1,Q2}. You only get the same utility if {Q1,Q3} is on the same IC, but it isn't.  I don't exactly see where the confusion is, but note that Q2 and Q3 are different quantities of the same good, otherwise we needed a 3-d graph.
Chris tie
<measuring-utility>
Why are there infinitely many indifference curves?
tsp216
# Why are there infinitely many indifference curves?

(Asked by: username_0 on 2017-01-21)

If an indifference curve shows quantities where a consumer's utility from consuming two goods are equal, then why are there infinitely many indifference curves? From the diagram, you can have Q1,Q2 on IC1, but then you'd have Q1,Q3 on the other indifference curve, wouldn't that mean the consumer would receive the same utility from consuming Q1 and Q2 as well as if he had consumed Q1 and Q3, i.e. for a given Q1, the consumption of Q2 gives the same amount of utility as Q3? Shouldn't this mean that the indifference curve should be unique?

[![enter image description here](https://i.sstatic.net/8xUcn.jpg)](https://i.sstatic.net/8xUcn.jpg)

**Tags:** measuring-utility

> **Comments:**
> **username_1**: "wouldn't that mean the consumer would receive the same utility from consuming Q1 and Q2 as well as if he had consumed Q1 and Q3" Why do  you think this...?  
> **username_0**: @denesp If the consumer is receiving 5 utilities from consuming q1 and 5 utilities from consuming q2, and q3 > q2, then how can he be receiving a 5 utilities from q3 as well? But isn't this what IC2 is suggesting, that the total utility of (q1,q2) is the same as (q1,q3)?  
> **username_1**: Why do you think he is receiving a 5 utilities from q3 as well? That is not in the definition of IC2 at all.  
> **username_2**: you do net get 5 utils from consuming q1! you get, let's say 5 utils from consuming the bundle {Q1,Q2}. You only get the same utility if {Q1,Q3} is on the same IC, but it isn't.  I don't exactly see where the confusion is, but note that Q2 and Q3 are different quantities of the same good, otherwise we needed a 3-d graph.  

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## 1 answers

### Answer by username_1 on 2017-01-21. Score: 2 | Accepted answer

Utility is constant for all points $(q\_B,q\_A)$ on an indifference curve. So there is a number $u\_1$ such that
$$
\forall (q\_B,q\_A) \in IC\_1: \ U(q\_B,q\_A) = u\_1.
$$
Similarly there is a number $u\_2$, such that
$$
\forall (q\_B,q\_A) \in IC\_2: \ U(q\_B,q\_A) = u\_2.
$$
If $IC\_1 \neq IC\_2$ then $u\_1 \neq u\_2$.


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