Explain the laws of returns to scale.

The law of returns to scale is a long-run law that shows what happens to total output when all inputs (labour and capital) are increased together in the same proportion, and it takes three forms.

1. Long-run setting: since all factors are variable in the long run, the firm changes its whole scale of operation rather than just factor proportions.
2. Assumptions: the producer is rational, only labour and capital are used, and both are increased in the same proportion.

Increasing returns to scale (IRS):

3. Meaning: output rises by a larger percentage than inputs (e.g. a 10% rise in inputs raises output by 20%).
4. Iso-quant spacing: successive equal-spaced iso-quants get closer together as output expands.
5. Causes: dimensional economies, greater specialisation, financial economies, and technical and managerial indivisibilities.

Constant returns to scale (CRS):

6. Meaning: output rises by exactly the same percentage as inputs (10% → 10%).
7. Iso-quant spacing: successive iso-quants are equally spaced.
8. Causes: optimum allocation of resources and the exhaustion of further economies of scale, so gains and losses balance out.

Decreasing returns to scale (DRS):

9. Meaning: output rises by a smaller percentage than inputs (10% → 8%); successive iso-quants get farther apart. It is caused by problems of coordination, management complexity and scarcity of some natural resources.
10. Nepal example: a small hydropower operation may more than double output when it first doubles turbines and staff (IRS), but at a very large scale coordination problems mean doubling inputs yields less than double the electricity (DRS).

Thus, returns to scale describe the long-run output response to a proportionate change in all inputs — increasing, constant or decreasing — depending on the economies and diseconomies operating at that scale.