<p>It is possible. Trivially if we have <span class="math-container">$Q^s=f(p)$</span> and <span class="math-container">$Q^d=g(p)$</span> and we plot this in a 3d-coordinate system with variables <span class="math-container">$p$</span>, <span class="math-container">$Q$</span> and some other variable <span class="math-container">$x$</span> (which does not appear in our functions at all), then we can take a 'slice' for every <span class="math-container">$x$</span>-value, and in fact every slice gives us the conventional 2d-depiction of this model.</p>

<p>We could of course take the standard supply-demand model and take some parameter as third variable, for example:</p>

<p><span class="math-container">$$Q^s(p,t)=\max(0, p-t), \quad Q^d(p,t)=\max(0, 1-p)$$</span></p>

<p>Where <span class="math-container">$t$</span> is a unit tax imposed on the suppliers of the good in question. We can plot this in a 3d coordinate system with variables <span class="math-container">$Q,t,p$</span> and a red line showing equilibria:</p>

<p><a href="https://i.sstatic.net/LycWA.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/LycWA.png" alt=""></a></p>

<p><a href="https://i.sstatic.net/mG5fw.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/mG5fw.png" alt=""></a></p>

<p>As we would expect there is a positive relationship between equilibrium price and the level of the unit tax.</p>

CC BY-SA 4.0
2020-01-25T15:24:03.873Z
2020-01-25T15:47:57.603Z
2020-01-25T15:47:57.603Z
user18214
<p>Is it possible ? if it's possible can someone give me a reference ? Thanks !</p>

<microeconomics><mathematical-economics>
Supply and Demand plotted on a three dimensional Cartesian coordinate system
Dika
# Supply and Demand plotted on a three dimensional Cartesian coordinate system

(Asked by: username_0 on 2020-01-25)

Is it possible ? if it's possible can someone give me a reference ? Thanks !

**Tags:** microeconomics, mathematical-economics


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## 1 answers

### Answer by username_1 on 2020-01-25. Score: 2 | Accepted answer

It is possible. Trivially if we have $Q^s=f(p)$ and $Q^d=g(p)$ and we plot this in a 3d-coordinate system with variables $p$, $Q$ and some other variable $x$ (which does not appear in our functions at all), then we can take a 'slice' for every $x$-value, and in fact every slice gives us the conventional 2d-depiction of this model.

We could of course take the standard supply-demand model and take some parameter as third variable, for example:

$$Q^s(p,t)=\max(0, p-t), \quad Q^d(p,t)=\max(0, 1-p)$$

Where $t$ is a unit tax imposed on the suppliers of the good in question. We can plot this in a 3d coordinate system with variables $Q,t,p$ and a red line showing equilibria:

[![](https://i.sstatic.net/LycWA.png)](https://i.sstatic.net/LycWA.png)

[![](https://i.sstatic.net/mG5fw.png)](https://i.sstatic.net/mG5fw.png)

As we would expect there is a positive relationship between equilibrium price and the level of the unit tax.


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