<p>In intro micro you usually assume that every firm in a perfectly competetive market has the same costs and production function etc. Hence, the MCs are the same for every firm. Under this assumptions, every firm will produce the same quantity in equilibrium.</p>

CC BY-SA 3.0
2016-08-11T14:43:41.930Z
2016-08-11T14:43:41.930Z
Pablo E
<p>Consider a perfectly competitive market with equilibrium price $P_{eq}$ and quantity $Q_{eq}$ and firm with profit maximising quantity $Q_f$ as illustrated below:</p>

<hr>

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

<hr>

<p>I guess any firm in the market would have the same demand, marginal revenue and average revenue (or am I wrong?), but what about profit maximising quantity $Q_f$? It seems to depend on $MC$. Is $MC$ different for each firm?</p>

<ol>
<li><p>If so, then $Q_f$ is not necessarily the same for each firm?</p></li>
<li><p>If not, why?</p></li>
</ol>

CC BY-SA 3.0
2016-08-11T14:46:55.313Z
This part: "any firm in the market would have the same demand" is not clear to me. The industry faces demand, not individual firms.
Giskard
CC BY-SA 3.0
2016-08-12T03:29:43.513Z
@denesp The MR for each firm is equal to the equilibrium price determined by the market right?
BCLC
CC BY-SA 3.0
2016-08-12T07:59:59.300Z
In a competitive market? Yes. I don't see what this has to do with demand though.
Giskard
<microeconomics><general-equilibrium><markets><competition><firm>
market equilibrium quantity $\ne$ firm profit maximising quantity?
BCLC
# market equilibrium quantity $\ne$ firm profit maximising quantity?

(Asked by: username_0 on 2016-08-10)

Consider a perfectly competitive market with equilibrium price $P\_{eq}$ and quantity $Q\_{eq}$ and firm with profit maximising quantity $Q\_f$ as illustrated below:

---

[![enter image description here](https://i.sstatic.net/FumUI.png)](https://i.sstatic.net/FumUI.png)

---

I guess any firm in the market would have the same demand, marginal revenue and average revenue (or am I wrong?), but what about profit maximising quantity $Q\_f$? It seems to depend on $MC$. Is $MC$ different for each firm?

1. If so, then $Q\_f$ is not necessarily the same for each firm?
2. If not, why?

**Tags:** microeconomics, general-equilibrium, markets, competition, firm
> **Comments:**
> **username_1**: This part: "any firm in the market would have the same demand" is not clear to me. The industry faces demand, not individual firms.  
> **username_0**: @denesp The MR for each firm is equal to the equilibrium price determined by the market right?  
> **username_1**: In a competitive market? Yes. I don't see what this has to do with demand though.  

---

## 1 answers

### Answer by username_2 on 2016-08-11. Score: 2 | Accepted answer

In intro micro you usually assume that every firm in a perfectly competetive market has the same costs and production function etc. Hence, the MCs are the same for every firm. Under this assumptions, every firm will produce the same quantity in equilibrium.


---

