Why is a production possibilities frontier typically drawn as a curve, rather than a straight line?

The Production Possibilities Frontier (PPF) is a graphical representation that shows the different combinations of two goods or services that an economy can produce efficiently given its limited resources and technology. In the PPF, the horizontal axis usually represents one good and the vertical axis represents the other good. As we move along the PPF, we assume that resources are being shifted from the production of one good to another, keeping everything else constant (ceteris paribus).

In economic models, there are two types of opportunity costs: constant and increasing. Constant opportunity costs mean that the resources can be transferred from the production of one good to another at a constant rate without any loss in productivity. This scenario results in a straight-line PPF. In contrast, increasing opportunity costs imply that as more resources are dedicated to the production of one good, the opportunity cost of producing the other good increases. This means that as we try to produce more of one good, we have to give up increasingly larger amounts of the other good. This typically occurs because resources are not perfectly adaptable between the two goods or industries.

In the real world, resources are often specialized, meaning they are more efficient at producing one good over another. As resources are transferred from the production of one good to another, the efficiency decreases, leading to increasing opportunity costs. A PPF is drawn as a curve rather than a straight line to reflect these increasing opportunity costs. The curve represents the maximal efficient output combinations. It is concave to the origin, which indicates that at any point along the PPF, resources are being allocated efficiently between the two goods, taking into account increasing opportunity costs. To sum up, a production possibilities frontier is typically drawn as a curve rather than a straight line because it represents the increasing opportunity costs associated with reallocating resources between the production of two goods, which is more in line with the real-world scenario of specialized resources and differing production efficiencies.