In a productive process, the relation between an equal proportional change in all inputs and the resulting proportional change in output. If a proportional increase of λ‎ in all inputs produces a proportional increase of λ‎ in output, there are constant returns to scale. If output rises by a larger proportion than inputs, there are increasing returns to scale. If output rises by a smaller proportion than inputs, there are decreasing returns to scale (this is different from the diminishing returns to scale.).