Cost Output Relationship in the Long Run
Cost Output Relationship in the Long Run
The long-run
cost-output implies the relationship between the changing scale of the firm and
the total output. In the long run, only the average cost is important and
considered in taking long term output decisions.
The long-run average cost is the long-run total cost divided by the level of output. It is the least possible cost of producing the given level of output when all the factors are variable. Long-run average cost curves will normally be U-shaped just as short-run curves are,
but they will always be flatter than the short-run ones. The reason is obvious
that the scale of operations of the firm can be changed and all the costs become
variable because there are no fixed factors in the long run. Over a long period,
the size of the plant can be changed, unwanted buildings can be sold, and
administrative and marketing staff can be increased or decreased to deal
efficiency and can be used more economically. Thus, the average cost will be lower
and variable costs will not rise as sharply as in a short period. That’s why
LAC curve is flatter than short-run ones.
The long-run
cost curves are influenced by the law of returns to scale. Each time the scale
of the operations of the firm is changed, a new short-run cost curve will have
to be drawn for the firm. In the short run, there will be only one AC curve to
represent one fixed scale of output and the short-run average cost curve [SAC] is
applicable to only one plant while the long-run average cost [LAC] takes many
plants into consideration because of the changes in the scale of operations.
LAC curve
will be tangent to all the SAC curves and will touch each SAC curve at its minimum point at optimum output. The LAC curve is also
known as the ‘Envelope Curve’ or
‘Planning Curve’ as it serves as a guide to the producer in his plans to
expand production.
Production
cost in the short and long run both:
In this
diagram, SAC1, SAC2, and SAC3 are the three possible plants and the LAC curve is
drawn according to these plants. For the output OQ1, plant SAC2 cost P1Q1 is
more than plant SAC1 R1Q1 which is a long-run cost also. For OQ2 output, the cost
will be the same [R2Q2] for the short run and long run both.
If the firm
increase the production OQ3, it can be obtained at the higher average cost P3Q3
in plant SAC2 but the same output OQ3 can be produced at a lower average cost
R3Q3 in the long run because the scale of the production can be modified in the
long-run according to the requirements.
Important
features of LAC and cost-output relationship in the long run:
- LAC curve will be tangent to all the SAC curves and will touch each SAC curve at its minimum point at the optimum output. SAC curve cannot be lower than the LAC curve for any given level of output.
- The LAC curve is also known as the ‘Envelope Curve’ because it envelops a group of SAC curves.
- The LAC curve is also known as the ‘Planning Curve’ as it serves as a guide to the producer in his plans to expand production and represents the least cost of production for the various possible level of output.
- Long-run average cost curves will normally be U-shaped or dish-shaped but they will always be flatter than the short-run ones.
- The LAC helps the producer to select the optimum size of the plant so that the factors can be utilized properly and economically.
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