Economic rent is the surplus of actual earnings over transfer earnings. Explain with suitable examples.

Economic rent, in the modern theory of rent propounded by Joan Robinson, is the surplus a factor of production earns over and above the minimum payment needed to keep it in its present use, i.e. the difference between its actual earning and its transfer earning.

1. Meaning: economic rent = actual earning − transfer earning, so it is the earning left over after the factor's minimum requirement is met.
2. Actual earning: the total economic value a factor earns in its current use.
3. Transfer earning: the minimum payment (the opportunity cost) needed to keep the factor in its present use, i.e. what it could earn in its next-best alternative.
4. All factors earn rent: unlike the classical view that only land earns rent, the modern theory holds that any factor — land, labour or capital — can earn economic rent depending on its supply.
5. Determined by demand and supply: the size of economic rent depends on the interaction of the demand for and supply of the factor, and especially on the elasticity of its supply.
6. Perfectly inelastic supply: when supply is completely fixed (like land, a non-reproducible gift of nature), transfer earning is zero, so the factor's entire earning is economic rent; the supply curve is vertical.
7. Perfectly elastic supply: when the supply curve is horizontal, actual earning exactly equals transfer earning, so there is no economic rent — every unit must be paid its transfer earning to stay.
8. Relatively elastic supply: when the supply curve slopes upward, the surplus above the factor's minimum earning is its economic rent, so the factor earns some rent but not its whole earning.
9. Example (land): prime commercial land in central Kathmandu is nearly fixed in supply, so almost its whole earning is economic rent — its owner earns a surplus simply because such land cannot be reproduced.
10. Example (labour): a film star or top cricketer who earns Rs. 50 lakh but would still work in the next-best job for Rs. 5 lakh earns Rs. 45 lakh of economic rent, since that surplus exceeds the transfer earning needed to keep them in the profession.

Thus, economic rent is the surplus of actual earnings over transfer earnings, arising because factor supply is not perfectly elastic — it is the whole earning when supply is fixed (land), nothing when supply is perfectly elastic, and a partial surplus when supply is relatively elastic.