If goods Y is substituted for goods X and MRS increases, then the goods X and Y will be:

Question

Accepted Answer

The correct option is 4:
The Marginal Rate of Substitution (MRS) refers to the amount of one good (Y) a consumer is willing to give up in order to obtain one additional unit of another good (X), while maintaining the same level of utility (staying on the same indifference curve). When the MRS increases as good Y is substituted for good X (meaning you are moving down the indifference curve and consuming more X and less Y), this implies that the two goods become increasingly valuable to each other as consumption is unbalanced. This is the definition of **Complementary Goods**. For complementary goods, the more you have of one (say, X), the greater the value of having the other (Y) alongside it, leading to a higher MRS when substituting towards the good you have less of. The indifference curve for complementary goods is generally more steeply curved or convex to the origin, reflecting the willingness to give up less and less of Y for each additional unit of X.

The incorrect option is 1:
Giffen goods are a type of inferior good where demand increases as price increases, violating the law of demand. The characteristics of the MRS do not directly determine whether a good is Giffen; this category relates to the relationship between price and quantity demanded.

The incorrect option is 2:
Substitute goods are those that can be used in place of one another, like tea and coffee. For substitutes, as you consume more X and substitute it for Y, the MRS should *decrease* (diminishing MRS), reflecting the fact that as you have more X, you are willing to give up less and less Y for another unit of X.

The incorrect option is 3:
Superior goods (or normal goods) are simply those for which demand increases as consumer income rises. The superior or inferior nature of a good relates to its income elasticity of demand, not directly to the behavior of the MRS between two different goods.