The production possibility curve (PPC) is a graphical representation of the different combinations of two goods that a country can produce with given resources and technology. PPC shows the maximum output that a country can produce with available resources and technology. The PPC curve is concave because of the law of diminishing marginal rate of substitution.


The law of diminishing marginal rate of substitution states that as a country produces more of a particular good, the opportunity cost of producing an additional unit of that good increases. This is because resources are not perfectly adaptable to producing either good. As more resources are allocated to producing one good, the opportunity cost of producing additional units of that good increases because resources are being taken away from the production of the other good.


The shape of the PPC curve reflects the opportunity cost of producing one good in terms of the other good. The PPC curve is concave because of the law of diminishing marginal rate of substitution. As a country produces more of a particular good, the opportunity cost of producing an additional unit of that good increases. This means that the slope of the PPC curve becomes steeper as we move from left to right along the curve.


The concave shape of the PPC curve has important implications for a country's production choices. A country can produce any combination of two goods that lie on or inside the PPC curve. Points on the PPC curve represent efficient use of resources, while points inside the PPC curve represent inefficient use of resources. A country can only produce outside the PPC curve if it can increase its resources or improve its technology.


In conclusion, the PPC curve is concave because of the law of diminishing marginal rate of substitution. The concave shape of the PPC curve reflects the opportunity cost of producing one good in terms of the other good. The PPC curve has important implications for a country's production choices.

PPC is concave to the origin because of increasing MRT. Increasing MRT means more and more unit of one good is to be sacrificed to get an additional unit of another good . and MRT is increasing because all the factors of production are not equally efficient in producing both the good.