When more units of a good or a service can be produced on a larger scale, yet with (on average) less input costs, economies of scale (ES) are said to be achieved. Alternatively, this means that as a company grows and production units increase, a company will have a better chance to decrease its costs. According to theory, economic growth may be achieved when economies of scale are realized.
Adam Smith identified the division of labor and specialization as the two key means to achieve a larger return on production. Through these two techniques, employees would not only be able to concentrate on a specific task, but with time, improve the skills necessary to perform their jobs. The tasks could then be performed better and faster. Hence, through such efficiency, time and money could be saved while production levels increased.
Just like there are economies of scale, diseconomies of scale (DS) also exist. This occurs when production is less than in proportion to inputs. What this means is that there are inefficiencies within the firm or industry resulting in rising average costs.
Internal and External Economies of Scale
Alfred Marshall made a distinction between internal and external economies of scale. When a company reduces costs and increases production, internal economies of scale have been achieved. External economies of scale occur outside of a firm, within an industry. Thus, when an industry's scope of operations expands due to, for example, the creation of a better transportation network, resulting in a subsequent decrease in cost for a company working within that industry, external economies of scale are said to have been achieved. With external ES, all firms within the industry will benefit.