1. The Theory and Estimation of Cost
The Importance of Cost in Managerial Decisions
The Definition and Use of Cost in Economic Analysis
The Relationship Between Production and Cost
The Short Run Cost Function
The Long Run Cost Function
The Learning Curve
Economies of Scope
Economies of Scale: the Short Run Versus the Long Run
Supply Chain Management
Ways Companies Have Cut Costs to Remain Competitive

2. Learning Objectives
Define the cost function and explain the difference between a short-run and a long-run cost function.
Explain the linkages between the production function and the cost function.
Distinguish between economic cost and accounting cost.
Explain how the concept of relevant cost is used in the economic analysis of cost.
Define short-run total cost, short-run variable cost, and total fixed cost and explain their relationship to each other.

3. Learning Objectives
Define average cost, average variable cost, and average fixed cost and explain their relationship to each other in the short run. Do the same for average cost and average variable cost in the long run.
Compare and contrast the short-run cost function and the long-run cost function and explain why economies of scale is considered to be a long-run phenomenon.
Provide at least four reasons for the existence of economies of scale.

4. The Importance of Cost in Managerial Decisions
Ways to contain or cut costs over the past decade
Most common: reduce number of people on the payroll
Outsourcing components of the business
Merge, consolidate, then reduce headcount

5. The Definition and Use of Cost in Economic Analysis
Relevant cost: a cost that is affected by a management decision.
Historical cost: cost incurred at the time of procurement.
Opportunity cost: amount or subjective value that is forgone in choosing one activity over the next best alternative.
Incremental cost: varies with the range of options available in the decision.
Sunk cost: does not vary in accordance with decision alternatives.

6. The Relationship Between Production and Cost
Cost function is simply the production function expressed in monetary rather than physical units.
Assume the firm is a “price taker” in the input market.

7. The Relationship Between Production and Cost
Total Variable Cost (TVC): the cost associated with the variable input, determined by multiplying the number of units by the unit price.
Marginal Cost (MC): the rate of change in total variable cost.
The law of diminishing returns implies that MC will eventually increase

8. The Relationship Between Production and Cost
Plotting TP and TVC illustrates that they are mirror images of each other.
When TP increases at an increasing rate, TVC increases at a decreasing rate.

9. The Short-Run Cost Function
For simplicity the following assumptions are made:
The firm employs two inputs, labor and capital.
The firm operates in a short-run production period where labor is variable, capital is fixed.
The firm uses the inputs to produce a single product.
The firm operates with a fixed level of technology.
The firm operates at every level of output in the most efficient way.
The firm operates in perfectly competitive input markets and must pay for its inputs at a given market rate. It is a “price taker” in the input markets.
The short-run production function is affected by the law of diminishing returns.

10. The Short-Run Cost Function
Standard variables in the short-run cost function:
Quantity (Q): the amount of output that a firm can produce in the short run.
Total fixed cost (TFC): the total cost of using the fixed input, capital (K)
Total variable cost (TVC): the total cost of using the variable input, labor (L)
Total cost (TC): the total cost of using all the firm’s inputs, L and K. TC = TFC + TVC

11. Total and Variable Costs
TC(Q): Minimum total cost of producing alternative levels of output:
TC(Q) = TVC(Q) + TFC
TVC(Q): Costs that vary with output.
TFC: Costs that do not vary with output. $ Q
C(Q) = VC + FC
VC(Q) FC

12. Fixed and Sunk Costs FC: Costs that do not change as output changes.$
FC: Costs that do not change as output changes.
Sunk Cost: A cost that is forever lost after it has been paid.
C(Q) = VC + FC
VC(Q) FC Q

13. The Short-Run Cost Function
Standard variables in the short-run cost function:
Average fixed cost (AFC): the average per-unit cost of using the fixed input K. AFC = TFC/Q
Average variable cost (AVC): the average per-unit cost of using the variable input L. AVC = TVC/Q
Average total cost (AC) is the average per-unit cost of using all the firm’s inputs. AC = AFC + AVC = TC/Q
Marginal cost (MC): the change in a firm’s total cost (or total variable cost) resulting from a unit change in output. MC = DTC/DQ = DTVC/DQ

14. Average Total Cost ATC = AVC + AFC ATC = C(Q)/Q $
Average Variable Cost
AVC = VC(Q)/Q
Average Fixed Cost
AFC = FC/Q
Marginal Cost
MC = DC/DQ $ Q MC
ATC
AVC MR
AFC

15. The Short-Run Cost Function
Important Observations
AFC declines steadily over the range of production.
When MC = AVC, AVC is at a minimum.
When MC < AVC, AVC is falling.
When MC > AVC, AVC is rising.
The same three rules apply for average cost (AC) as for AVC.

16. The Short-Run Cost Function
A reduction in the firm’s fixed cost would cause the average cost line to shift downward.
A reduction in the firm’s variable cost would cause all three cost lines (AC, AVC, MC) to shift.

17. Fixed Cost MC $ ATC AVC ATC Fixed Cost AFC AVC Q Q0 Q0(ATC-AVC)
= Q0 AFC
= Q0(FC/ Q0)
= FC MC $ Q
ATC
AVC
ATC
Fixed Cost
AFC
AVC Q0

18. Variable Cost MC $ ATC AVC AVC Variable Cost Q Q0 Q0AVC
= Q0[VC(Q0)/ Q0]
= VC(Q0) $ Q
ATC
AVC
AVC
Variable Cost Q0

19. Total Cost MC $ ATC AVC ATC Total Cost Q Q0 Q0ATC = Q0[C(Q0)/ Q0]

20. The Short-Run Cost Function
Alternative specifications of the Total Cost function
Most commonly: specified as a cubic relationship between total cost and output
As output increases, total cost first increases at a decreasing rate, then increases at an increasing rate.
Quadratic relationship
As output increases, total cost increases at an increasing rate.
Linear relationship
As output increases, total cost increases at a constant rate.

21. Cubic Cost Function C(Q) = f + a Q + b Q2 + cQ3 Marginal Cost?
Memorize:
MC(Q) = a + 2bQ + 3cQ2
Calculus:
dC/dQ = a + 2bQ + 3cQ2

22. An Example Total Cost: C(Q) = 10 + Q + Q2 Variable cost function:
VC(Q) = Q + Q2
Variable cost of producing 2 units:
VC(2) = 2 + (2)2 = 6
Fixed costs:
FC = 10
Marginal cost function:
MC(Q) = 1 + 2Q
Marginal cost of producing 2 units:
MC(2) = 1 + 2(2) = 5

23. The Long-Run Cost Function
In the long run, all inputs to a firm’s production function may be changed.
Because there are no fixed inputs, there are no fixed costs.
The firm’s long run marginal cost pertains to returns to scale.
First, increasing returns to scale.
As firms mature, they achieve constant returns, then ultimately decreasing returns to scale.

24. The Long-Run Cost Function
When a firm experiences increasing returns to scale:
A proportional increase in all inputs increases output by a greater proportion.
As output increases by some percentage, total cost of production increases by some lesser percentage.

25. The Long-Run Cost Function
Economies of Scale: situation where a firm’s long-run average cost (LRAC) declines as output increases.
Diseconomies of Scale: situation where a firm’s LRAC increases as output increases.
In general, the LRAC curve is u-shaped.

26. Economies of Scale $
LRAC
Economies
of Scale
Diseconomies
of Scale Q

27. The Long-Run Cost Function
Reasons for long-run economies
Specialization in the use of labor and capital.
Prices of inputs may fall as the firm realizes volume discounts in its purchasing.
Use of capital equipment with better price-performance ratios.
Larger firms may be able to raise funds in capital markets at a lower cost than smaller firms.
Larger firms may be able to spread out promotional costs.

28. The Long-Run Cost Function
Reasons for Diseconomies of Scale
Scale of production becomes so large that it affects the total market demand for inputs, so input prices rise.
Transportation costs tend to rise as production grows.
Handling expenses, insurance, security, and inventory costs affect transportation costs.

29. The Long-Run Cost Function
In long run, the firm can choose any level of capacity.
Once it commits to a level of capacity, at least one of the inputs must be fixed. This then becomes a short-run problem.
The LRAC curve is an envelope of SRAC curves, and outlines the lowest per-unit costs the firm will incur over a range of output.

30. The Learning Curve
Learning Curve: line showing the relationship between labor cost and additional units of output.
Downward slope indicates additional cost per unit declines as the level of output increases because workers improve with practice.
Measured in terms of percentage decrease in additional labor cost as output doubles.
Yx = Kxn
Yx = Units of factor or cost to produce the xth unit
K = Factor units or cost to produce the Kth (usually first) unit
x = Product unit (the xth unit)
n = log S/log 2
S = Slope parameter

31. Economies of Scope
Economies of Scope: reduction of a firm’s unit cost by producing two or more goods or services jointly rather than separately.
Closely related to economies of scale.

32. Multi-Product Cost Function
C(Q1, Q2): Cost of jointly producing two outputs.
General function form:

33. TC(Q1, 0) + TC(0, Q2) > TC(Q1, Q2).
Economies of Scope
TC(Q1, 0) + TC(0, Q2) > TC(Q1, Q2).
It is cheaper to produce the two outputs jointly instead of separately.
Example:
It is cheaper for Time-Warner to produce Internet connections and Instant Messaging services jointly than separately.

34. DMC1(Q1,Q2) /DQ2 < 0. Cost Complementarity
The marginal cost of producing good 1 declines as more of good two is produced:
DMC1(Q1,Q2) /DQ2 < 0.
Example:
Cow hides and steaks.

35. Quadratic Multi-Product Cost Function
TC(Q1, Q2) = f + aQ1Q2 + (Q1 )2 + (Q2 )2
MC1(Q1, Q2) = aQ2 + 2Q1
MC2(Q1, Q2) = aQ1 + 2Q2
Cost complementarity: a < 0
Economies of scope: f > aQ1Q2
TC(Q1 ,0) + TC(0, Q2 ) = f + (Q1 )2 + f + (Q2)2
f > aQ1Q2: Joint production is cheaper

36. A Numerical Example: TC(Q1, Q2) = 90 - 2Q1Q2 + (Q1 )2 + (Q2 )2
Cost Complementarity?
Yes, since a = -2 < 0
MC1(Q1, Q2) = -2Q2 + 2Q1
Economies of Scope?
Yes, since 90 > -2Q1Q2

37. Supply Chain Management
Supply Chain Management (SCM): efforts by a firm to improve efficiencies through each link of a firm’s supply chain from supplier to customer.
Includes all internal and external activities required to fulfill a customer’s demand.
Transaction costs are incurred by using resources outside the firm.
Coordination costs arise because of uncertainty and complexity of tasks.
Information costs arise because information is essential to the proper coordination of activities between the firm and its suppliers.

38. Supply Chain Management
Ways to develop better supplier relationships
Strategic alliance: firm and outside supplier join together in some sharing of resources.
Competitive tension: firm uses two or more suppliers, thereby helping the firm keep its purchase prices under control.

39. Ways Companies Have Cut Costs to Remain Competitive
The Strategic Use of Cost
Reduction in Cost of Materials
Using Information Technology to Reduce Costs
Reduction of Process Costs
Relocation to Lower-Wage Countries or Regions
Mergers, Consolidation, and Subsequent Downsizing
Layoffs and Plant Closings