<p>In my <a href="https://rads.stackoverflow.com/amzn/click/com/1510421270" rel="nofollow noreferrer" rel="nofollow noreferrer">economics book*</a>, in the lesson explaining what price elasticity of supply is, it's written:</p>
<blockquote>
<p><em>Any supply curve that starts at the origin has a PES value equal to 1. The theoretical outcome means that a change in price causes the same proportional change in quantity supplied.</em></p>
</blockquote>
<p><img src="https://i.sstatic.net/3TyUs.jpg" alt="enter image description here" /></p>
<p>Why do supply curves that start at the origin have a PES value of 1?</p>
<p>Why can't the supply curve start at somewhere else on the x-axis and still have a price elasticity of 1?</p>
<p>*Section 2. Chapter 12. Page 59</p>

CC BY-SA 4.0
2021-08-21T11:44:26.213Z
Thank you for the edit. The statement is only true for linear supply functions. Do you know the PES formula, and if yes did you try to apply it?
Giskard
CC BY-SA 4.0
2021-08-21T12:14:40.367Z
Yes, it's PES= %∆Qs/%∆P. But I don't follow how it'll help me. Why can't the line start at any point on the x-axis or y-axis and still have a unitary price elasticity supply? Or at least have the line hanging and not touching any of the axes since it's illogical for the suppliers to be willingly to supply anything when the price is zero.
Manar
CC BY-SA 4.0
2021-08-21T12:22:06.900Z
A line starting at the origin will have equation $S(p) = a \cdot p$. A line starting on the $y$-axis will be $S(p) = a \cdot p + b$ with $b \neq 0$. Try applying the formula?
Giskard
<supply-and-demand><elasticity>
Why do supply curves that start at the origin have a PES value of 1?
Manar
# Why do supply curves that start at the origin have a PES value of 1?

(Asked by: username_0 on 2021-08-20)

In my [economics book\*](https://rads.stackoverflow.com/amzn/click/com/1510421270), in the lesson explaining what price elasticity of supply is, it's written:

> *Any supply curve that starts at the origin has a PES value equal to 1. The theoretical outcome means that a change in price causes the same proportional change in quantity supplied.*

![enter image description here](https://i.sstatic.net/3TyUs.jpg)

Why do supply curves that start at the origin have a PES value of 1?

Why can't the supply curve start at somewhere else on the x-axis and still have a price elasticity of 1?

\*Section 2. Chapter 12. Page 59

**Tags:** supply-and-demand, elasticity

> **Comments:**
> **username_1**: Thank you for the edit. The statement is only true for linear supply functions. Do you know the PES formula, and if yes did you try to apply it?  
> **username_0**: Yes, it's PES= %∆Qs/%∆P. But I don't follow how it'll help me. Why can't the line start at any point on the x-axis or y-axis and still have a unitary price elasticity supply? Or at least have the line hanging and not touching any of the axes since it's illogical for the suppliers to be willingly to supply anything when the price is zero.  
> **username_1**: A line starting at the origin will have equation $S(p) = a \cdot p$. A line starting on the $y$-axis will be $S(p) = a \cdot p + b$ with $b \neq 0$. Try applying the formula?  

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## 0 answers

