# ⓘ Marginal value. A marginal value is the change in a value associated with a specific change in some independent variable, whether it be of that variable or of a ..

## ⓘ Marginal value

A marginal value is

• the change in a value associated with a specific change in some independent variable, whether it be of that variable or of a dependent variable, or
• a value that holds true given particular constraints,
• the ratio of the change of a dependent variable to that of the independent variable.

This third case is actually a special case of the second.

In the case of differentiability, at the limit, a marginal change is a mathematical differential, or the corresponding mathematical derivative.

These uses of the term" marginal” are especially common in economics, and result from conceptualizing constraints as borders or as margins. The sorts of marginal values most common to economic analysis are those associated with unit changes of resources and, in mainstream economics, those associated with infinitesimal changes. Marginal values associated with units are considered because many decisions are made by unit, and marginalism explains unit price in terms of such marginal values. Mainstream economics uses infinitesimal values in much of its analysis for reasons of mathematical tractability.

### 1.1. Quantified conception Discrete change

If the value of x i {\displaystyle x_{i}} is discretely changed from x i, 0 {\displaystyle x_{i,0}} to x i, 1 {\displaystyle x_{i,1}} while other independent variables remain unchanged, then the marginal value of the change in x i {\displaystyle x_{i}} is

Δ x i = x i, 1 − x i, 0 {\displaystyle \Delta x_{i}=x_{i,1}-x_{i,0}}

and the" marginal value” of y {\displaystyle y} may refer to

Δ y = f − f {\displaystyle \Delta y=f\leftx_{1},x_{2},\ldots,x_{i,1},\ldots,x_{n}\right-f\leftx_{1},x_{2},\ldots,x_{i,0},\ldots,x_{n}\right}

or to

Δ y Δ x = f − f x i, 1 − x i, 0 {\displaystyle {\frac {\Delta y}{\Delta x}}={\frac {f\leftx_{1},x_{2},\ldots,x_{i,1},\ldots,x_{n}\right-f\leftx_{1},x_{2},\ldots,x_{i,0},\ldots,x_{n}\right}{x_{i,1}-x_{i,0}}}}

### 1.2. Quantified conception Example

If an individual saw her income increase from $50000 to$55000 per annum, and part of her response was to increase yearly purchases of amontillado from 2 casks to three casks, then

• the marginal increase in her income was $5000 • the marginal effect on her purchase of amontillado was an increase of 1 cask, or of 1 cask per$5000.

### 1.3. Quantified conception Infinitesimal margins

If infinitesimal values are considered, then a marginal value of x i {\displaystyle x_{i}} would be d x i {\displaystyle dx_{i}}, and the" marginal value” of y {\displaystyle y} would typically refer to

∂ y ∂ x i = ∂ f ∂ x i {\displaystyle {\frac {\partial y}{\partial x_{i}}}={\frac {\partial f\leftx_{1},x_{2},\ldots,x_{n}\right}{\partial x_{i}}}}

For a linear functional relationship y = a + b ⋅ x {\displaystyle y=a+b\cdot x}, the marginal value of y {\displaystyle y} will simply be the co-efficient of x {\displaystyle x} in this case, b {\displaystyle b} and this will not change as x {\displaystyle x} changes. However, in the case where the functional relationship is non-linear, say y = a ⋅ b x {\displaystyle y=a\cdot b^{x}}, the marginal value of y {\displaystyle y} will be different for different values of x {\displaystyle x})

### 1.4. Quantified conception Example

Assume that, in some economy, aggregate consumption is well-approximated by

C = C Y {\displaystyle C=C\leftY\right}

where

• Y {\displaystyle Y} is aggregate income.

Then the marginal propensity to consume is

M P C = d C d Y {\displaystyle MPC={\frac {dC}{dY}}}

• diminishing marginal utility is at the heart of the explanation of numerous economic phenomena, including time preference and the value of goods .
• Marginalism is a theory of economics that attempts to explain the discrepancy in the value of goods and services by reference to their secondary, or marginal
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• the values of the other variables. Marginal variables are those variables in the subset of variables being retained. These concepts are marginal because
• by the individual himself or herself. A value that holds true given particular constraints is a marginal value A change that would be affected as or by
• series Marginal seat or marginal constituency or marginal in politics Marginalism Marginal analysis Marginal concepts Marginal cost Marginal demand Marginal
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• between price and marginal cost. The formula states that markup as a percentage of price equals the negative and hence the absolute value of the inverse
• In economics, the marginal product of labor MPL is the change in output that results from employing an added unit of labor. It is a feature of the production