<p>Yes.</p>
<p>I have to include at least 30 characters in an answer, so let me repeat: Yes.</p>

CC BY-SA 4.0
2021-05-12T16:58:42.537Z
Cheers. I feel very much confirmed now indeed.
j3141592653589793238
CC BY-SA 4.0
2021-05-12T13:36:14.703Z
2021-05-12T13:36:14.703Z
VARulle
<p>This will be a weird answer:</p>
<hr />
<p>As we know that <span class="math-container">$Q*P=const.$</span> for Cobb-Douglas preferences.</p>
<p><span class="math-container">$$
QP=const. \implies 0=d(PQ)=Q\ dP+P\ dQ \implies \frac{dQ}{Q}=-\frac{dP}{P}
$$</span>
thus we can conclude that <span class="math-container">$\frac{dQ/Q}{dP/P}$</span> is always <span class="math-container">$-1$</span>.</p>

CC BY-SA 4.0
2021-05-12T10:35:22.293Z
@j3141592653589793238 I still don't know what you were asking, I copied the answer from the body of your question.
Giskard
CC BY-SA 4.0
2021-05-12T10:35:49.190Z
I'm asking whether the assumption about Cobb-Douglas preferences always leading to iso-elastic demand curves is correct. Should I avoid such yes/no questions? Sorry. I just wasn't  quite sure. @Giskard
j3141592653589793238
CC BY-SA 4.0
2021-05-12T10:37:10.250Z
The part that puzzles me is how you could not decide based on the evidence you yourself gave. I gave the same reasoning as you did; how was this helpful?
Giskard
CC BY-SA 4.0
2021-05-12T10:39:06.050Z
I didn't know if the approach was correct and I'm still learning and I couldn't find a passage in my textbook that said that explicitly.
j3141592653589793238
CC BY-SA 4.0
2021-05-12T10:40:12.237Z
Allright. If you feel my copying the body of your question into an answer helped, you are welcome.
Giskard
CC BY-SA 4.0
2021-05-12T10:41:55.253Z
Sure, just needed some confirmation from a professional! :) @Giskard
j3141592653589793238
CC BY-SA 4.0
2021-05-12T13:37:41.083Z
I added an answer for extra confirmation ;-)
VARulle
CC BY-SA 4.0
2021-05-12T10:33:32.790Z
2021-05-12T10:33:32.790Z
Giskard
<p>As we know that <span class="math-container">$Q*P=const.$</span> for Cobb-Douglas preferences, we can thus conclude that <span class="math-container">$\frac{dQ/Q}{dP/P}$</span> is always <span class="math-container">$-1$</span>:</p>
<p><span class="math-container">$$
QP=const. \implies 0=d(PQ)=Q\ dP+P\ dQ \implies \frac{dQ}{Q}=-\frac{dP}{P}
$$</span></p>

<microeconomics><utility><elasticity><cobb-douglas>
Is it true that for Cobb-Douglas preferences, the demand function is always iso-elastic?
j3141592653589793238
# Is it true that for Cobb-Douglas preferences, the demand function is always iso-elastic?

(Asked by: username_0 on 2021-05-12)

As we know that $Q\*P=const.$ for Cobb-Douglas preferences, we can thus conclude that $\frac{dQ/Q}{dP/P}$ is always $-1$:

$$
QP=const. \implies 0=d(PQ)=Q\ dP+P\ dQ \implies \frac{dQ}{Q}=-\frac{dP}{P}
$$

**Tags:** microeconomics, utility, elasticity, cobb-douglas

---

## 2 answers

### Answer by username_2 on 2021-05-12. Score: 3 | Accepted answer

This will be a weird answer:

---

As we know that $Q\*P=const.$ for Cobb-Douglas preferences.

$$
QP=const. \implies 0=d(PQ)=Q\ dP+P\ dQ \implies \frac{dQ}{Q}=-\frac{dP}{P}
$$
thus we can conclude that $\frac{dQ/Q}{dP/P}$ is always $-1$.

> **Comments:**
> **username_2**: @j3141592653589793238 I still don't know what you were asking, I copied the answer from the body of your question.  
> **username_0**: I'm asking whether the assumption about Cobb-Douglas preferences always leading to iso-elastic demand curves is correct. Should I avoid such yes/no questions? Sorry. I just wasn't  quite sure. @Giskard  
> **username_2**: The part that puzzles me is how you could not decide based on the evidence you yourself gave. I gave the same reasoning as you did; how was this helpful?  
> **username_0**: I didn't know if the approach was correct and I'm still learning and I couldn't find a passage in my textbook that said that explicitly.  
> **username_2**: Allright. If you feel my copying the body of your question into an answer helped, you are welcome.  
> **username_0**: Sure, just needed some confirmation from a professional! :) @Giskard  
> **username_1**: I added an answer for extra confirmation ;-)  

---

### Answer by username_1 on 2021-05-12. Score: 4

Yes.

I have to include at least 30 characters in an answer, so let me repeat: Yes.

> **Comments:**
> **username_0**: Cheers. I feel very much confirmed now indeed.  

---

