<p><strong>Marginal utility</strong> is, by definition, <strong>the additional utility that comes from consuming an additional unit of a good</strong> (more precisely, this holds if we  consider discrete units of the good, if we have a continuous differentiable utility function marginal utility is  the derivative of the function, but the intuitive concept is the same).</p>
<p>Therefore, if <strong>marginal utility is (strictly, that is not zero) positive,</strong> this means that the consumption of an additional unit of the good <strong>increases</strong>  total utility.</p>
<p>In order to have a <strong>decrease of total utility</strong>, we must have a (strictly) <strong>negative marginal utility</strong>.</p>
<p>Therefore, the correct statement is just the contrary of what you said: <strong>if marginal utility is positive, an additional unit of a product will cause the total utility to increase.</strong></p>

CC BY-SA 4.0
2023-03-13T17:43:29.127Z
If I consider the Law of diminishing marginal utility, then is the statement still false?
raf raf
CC BY-SA 4.0
2023-03-13T17:48:42.673Z
Yes, that Law doesn't change the fact that the mariginal utility is positive, it means that it is positive, but  decreasing, smaller  as long as the consumption increases, but still positive. From a  technical point of view this law involves the second derivative, not the derivative: the first derivative is positive, the second derivative is negative (but the second derivative only).
BakerStreet
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2023-03-14T00:20:56.890Z
That means, Total Utility increases but in a declining rate if i consider Law of diminishing utility ?
raf raf
CC BY-SA 4.0
2023-03-14T00:30:00.410Z
Yes, exactly.  That's the meaning of the law of diminishing marginal utility.
BakerStreet
CC BY-SA 4.0
2023-03-13T17:38:37.580Z
2023-03-13T17:38:37.580Z
BakerStreet
<p>The statement is not true. Consider trivial example of following utility function:</p>
<p><span class="math-container">$$U= 2x^{0.5}$$</span></p>
<p>Marginal utility will be always positive for this for this function (given that x is a good so <span class="math-container">$x\geq 0$</span>, you can check that MU is</p>
<p><span class="math-container">$$MU = \frac{1}{x^{0.5}}$$</span></p>
<p>which will always be positive in this case yet consuming additional units of x causes <span class="math-container">$U$</span> to increase not decrease.</p>

CC BY-SA 4.0
2023-03-13T16:17:47.783Z
2023-03-13T18:52:00.200Z
2023-03-13T18:52:00.200Z
1muflon1
<p>If marginal utility is positive, consuming an additional unit of a product will cause total utility to decline. Is that statement true and why?</p>

<microeconomics>
Marginal utility vs Total utility
raf raf
# Marginal utility vs Total utility

(Asked by: username_0 on 2023-03-13)

If marginal utility is positive, consuming an additional unit of a product will cause total utility to decline. Is that statement true and why?

**Tags:** microeconomics

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## 2 answers

### Answer by username_1 on 2023-03-13. Score: 2

**Marginal utility** is, by definition, **the additional utility that comes from consuming an additional unit of a good** (more precisely, this holds if we consider discrete units of the good, if we have a continuous differentiable utility function marginal utility is the derivative of the function, but the intuitive concept is the same).

Therefore, if **marginal utility is (strictly, that is not zero) positive,** this means that the consumption of an additional unit of the good **increases** total utility.

In order to have a **decrease of total utility**, we must have a (strictly) **negative marginal utility**.

Therefore, the correct statement is just the contrary of what you said: **if marginal utility is positive, an additional unit of a product will cause the total utility to increase.**

> **Comments:**
> **username_0**: If I consider the Law of diminishing marginal utility, then is the statement still false?  
> **username_1**: Yes, that Law doesn't change the fact that the mariginal utility is positive, it means that it is positive, but  decreasing, smaller  as long as the consumption increases, but still positive. From a  technical point of view this law involves the second derivative, not the derivative: the first derivative is positive, the second derivative is negative (but the second derivative only).  
> **username_0**: That means, Total Utility increases but in a declining rate if i consider Law of diminishing utility ?  
> **username_1**: Yes, exactly.  That's the meaning of the law of diminishing marginal utility.  

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### Answer by username_2 on 2023-03-13. Score: 0

The statement is not true. Consider trivial example of following utility function:

$$U= 2x^{0.5}$$

Marginal utility will be always positive for this for this function (given that x is a good so $x\geq 0$, you can check that MU is

$$MU = \frac{1}{x^{0.5}}$$

which will always be positive in this case yet consuming additional units of x causes $U$ to increase not decrease.


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