Returns to scale pertains to variations in output due to a relative change in the inputs, that is, an increase of all inputs by an invariant factor. Whenever output shoots up by an identical margin, it is followed by constant returns to scale (CRTS).
On the other hand, in the event of an increase in output by less than the proportional change, decreasing returns to scale (DRS) take effect. While output increases to a by a higher margin, translates to increasing returns to scale (IRS)
The returns to scale and the concept of economies of scale are defined in the production theory of business administration and in the micro economy as the dependence of production on the amount inserted factors of production. Constant returns to scale relates to a proportional change in the input factors.
The assumption of constant returns to scale are not always fulfilled. This is the case when doubling the use of these factors, i.e. in duplication and more efficient use of input factors, the output would be more than double.
Returns to scale outline the rate at which the output increases in relation to proportional increases in inputs. It is therefore, an indicator of how the output responds when all factors are increasingly used in the same initiating ratio.
Economies of scale, however, are the effects that result from increasing or decreasing returns to scale. In practice, yields are commonly increasing for small quantities to become constant, then decreasing for very large quantities. And there is an optimum size for a company, which helps maximize returns.
Yields decrease whenever output varies less than the variation of inputs used. This means that the marginal cost is increasing or that more factors are needed to produce a unit. When the returns become negative, it is considered to be waste of scale or dis-economies of scale.
In the context of economies of scale, there are other terms that are very similar, but are distinguished from each other. First, there is the concept of economies of scale, and then the concept of economies of scope.
Economies of scale often apply in industries which have high capital costs spread over a big number of units of production. The application of economies of scale assists in illustrating the reasons behind the exceptional growth of companies in some areas of business.
It also forms the basis of justification for free trade policies, because some economies of scale could demand a bigger market, that maybe inconceivable in a given national territory. Economies of scale constitute one of three basic principles of urban economy with externalities and transport costs. And it is also part of the principle of the new economic geography (NEG).