Why is Rent restricted to land?

Land is fixed in supply. Because land cannot be produced, its behavior in markets is essentially different from things that can be produced. Many modern economists point out that some things other than land can be fixed in supply; examples include individual works of art, or the services of famous movie stars. However, such things are produced by labor, and are therefore still fundamentally different from natural opportunities. Also, land is always fixed in supply, while the vast majority of labor or capital are not. This is why, in this course, we restrict the term "Economic Rent" to the income gained from granting access to land.