A law of economics stating that as a person increases consumption of a product - while keeping consumption of other products constant - there is a decline in the marginal utility that person derives from consuming each additional unit of that product.
EXPLANATION
This is the premise on which buffet-style restaurants operate. They entice you with "all you can eat," all the while knowing each additional plate of food provides less utility than the one before. And despite their enticement, most people will eat only until the utility they derive from additional food is slightly lower than the original.
For example, say you go to a buffet and the first plate of food you eat is very good. On a scale of ten you would give it a ten. Now your hunger has been somewhat tamed, but you get another full plate of food. Since you're not as hungry, your enjoyment rates at a seven at best. Most people would stop before their utility drops even more, but say you go back to eat a third full plate of food and your utility drops even more to a three. If you kept eating, you would eventually reach a point at which your eating makes you sick, providing dissatisfaction, or 'dis-utility'.
The Law of Diminishing Marginal Utility - The law of diminishing marginal utility can be logically deduced from the axiom of human action. To show this, let us start with some remarks on utility.Utility is a subjective concept. It denotes "satisfaction" (or "happiness" or "contentment"). It rises if and when an individual increases his or her state of satisfaction. Conversely, if and when someone considers himself in a worse state of affairs, his utility decreases.
What is more, utility is an ordinal concept, meaning that utility cannot be measured in terms of higher or lower utility from the viewpoint of an individual; and changes in utility among different people cannot be measured. All one can say is that utility is higher or lower from the viewpoint of an