Source: Wilkerson Company case, Managerial/Cost Accounting (University of Texas at Austin)
Tags: Wilkerson, activity-based costing, ABC, traditional costing, overhead allocation, cost distortion, product costing, managerial accounting, cost accounting, production overhead, direct labour, machine hours
Difficulty: Intermediate | Prerequisites: Basic understanding of cost accounting terminology (direct materials, direct labour, overhead, gross margin).
Big Picture
This case sits at the heart of managerial accounting: how a company allocates overhead costs to its products, and what happens when that allocation is wrong. Wilkerson makes three products (valves, pumps, flow controllers) using the same equipment and labour, but each product consumes resources differently. The company's traditional cost system uses a single overhead rate based on direct labour dollars, which masks the true cost of each product. Understanding this case prepares you to evaluate when a simple cost system breaks down and when activity-based costing (ABC) provides better information for pricing and product-mix decisions.
Wilkerson allocates all overhead as 300% of direct labour cost, which over-costs high-volume simple products (valves) and under-costs complex low-volume products (flow controllers). Switching to activity-based costing reveals that flow controllers are far more profitable than the traditional system suggests, while pumps may actually be losing money. The case is a classic illustration of why single-rate overhead allocation distorts product costs and leads to poor pricing decisions.
Direct materials
The raw or semi-finished components purchased and used in producing a product. In Wilkerson's case, these are the machined components bought from suppliers.
In simple terms, this is the physical stuff that goes into making each unit.
Direct labour
The cost of workers who physically produce the product, charged at a standard rate per hour. Wilkerson uses $25 per hour.
Think of it as the wages you can trace straight to a specific product being made.
Overhead (manufacturing overhead)
All production costs that are not direct materials or direct labour: machine depreciation, set-up costs, shipping and packaging, engineering support, facility costs. At Wilkerson, overhead is 300% of direct labour cost.
In simple terms, everything it costs to run the factory that you cannot pin directly to one unit of product.
Overhead allocation rate
The percentage or rate used to assign overhead costs to products. Wilkerson's rate is 300% of production-run direct labour costs, meaning for every $1 of direct labour, $3 of overhead is charged.
Think of it as the multiplier that spreads shared factory costs across products.
Activity-based costing (ABC)
A costing method that assigns overhead to products based on the activities that actually drive those costs (machine hours, number of set-ups, number of shipments), rather than a single blanket rate.
In simple terms, instead of one big bucket of overhead split by labour, you figure out what actually causes each type of overhead and charge accordingly.
Cost driver
The factor that causes an overhead cost to be incurred. Examples: machine hours drive machine-related overhead; the number of production runs drives set-up costs; the number of shipments drives packaging and shipping costs.
Think of it as the "why" behind each overhead expense.
Gross margin
Revenue minus cost of goods sold, expressed as a percentage of revenue. Wilkerson's reported gross margins are 35% for valves, 20% for pumps, and above 10% for flow controllers (under the traditional system).
In simple terms, how much of each sales dollar is left after covering production costs.
Production run (batch)
A single cycle of manufacturing a group of components. Each run requires a set-up regardless of batch size, so short runs carry a higher per-unit set-up cost than long runs.
Think of it as one "session" on a machine to produce a batch of parts.
Cost distortion
The misallocation of costs that occurs when a simple overhead rate is applied uniformly to products that consume resources in very different ways. High-volume, simple products get over-costed; low-volume, complex products get under-costed.
In simple terms, the numbers look right in total but are wrong for each individual product.
The company and its products
Wilkerson supplies components to manufacturers of water purification equipment
Three product lines, all using the same equipment and labour:
Valves – four machined components, standard design, shipped in large volumes, 35% gross margin
Pumps – five machined components, sold through industrial distributors, 20% gross margin (kept low to maintain market share)
Flow controllers – more components and more labour than valves or pumps, customised, priced at above 10% over cost
The production process
Starts with purchasing semi-finished components from suppliers
Components are machined in-house to meet specifications
All three product lines share a single production department
Workers often operate several machines simultaneously
The traditional cost system
Unit cost = direct materials + direct labour
Material costs are based on prices paid under annual purchasing agreements
Labour is charged at $25 per hour, based on standard time per product
Overhead is allocated at 300% of direct labour cost
One producing department, one allocation rate for everything
This is a textbook example of a "peanut butter" cost system: overhead is spread evenly across products regardless of how differently each product actually uses factory resources.
What went wrong
Overhead costs were significantly larger than direct labour, yet the allocation was based entirely on labour dollars
Severe price cutting on pumps was eroding profits, but the cost system could not show whether pumps were truly unprofitable or just under-priced
The 300% rate treats every labour dollar as equally responsible for overhead, ignoring that different products drive overhead in different ways
Key observations from the production floor
Workers operate multiple machines at once, so labour hours are a poor proxy for machine usage
Every production run requires a set-up, regardless of batch size: short runs cost as much to set up as long runs
Shipping and packaging effort is driven by the number of shipments, not by the volume shipped
These observations point to a mismatch: the cost drivers that actually cause overhead (machine time, number of set-ups, number of shipments) are not the basis the system uses to allocate it.
The ABC fix
Replace the single 300% labour-based rate with multiple cost pools, each tied to its own driver:
Machine-related overhead allocated by machine hours
Set-up costs allocated by number of production runs
Shipping and receiving costs allocated by number of shipments
General overhead allocated by a more appropriate base (potentially machine hours or another driver)
The result: products that use more machine time, require more set-ups, or generate more shipments absorb more overhead
What ABC reveals
Valves are likely over-costed under the traditional system (high volume, long production runs, fewer set-ups per unit)
Pumps may be more profitable than the 20% margin suggests, or may genuinely be under-priced, depending on how overhead shifts under ABC
Flow controllers are likely under-costed under the traditional system (low volume, many set-ups, more shipments per unit, heavy machine use), meaning their true margin is lower than reported
Strategic recommendations from the case
Recalculate product costs using machine hours rather than labour hours as the primary allocation base
Re-evaluate pump pricing: the competitive pressure to cut prices may be justified if true costs are lower than reported, or it may be destroying value if true costs are higher
Consider shifting product mix toward flow controllers, where the company has pricing power and customisation creates a defensible position
The suggestion to drop valves entirely is aggressive; a better first step is to reprice using accurate cost data
Traditional overhead allocation
Overhead charged to a product = Direct labour cost x 300%
Unit cost = Direct materials + Direct labour + Overhead allocated
ABC overhead allocation (conceptual)
For each cost pool:
Cost pool rate = Total cost in pool / Total quantity of cost driver
Overhead per unit from that pool = Cost pool rate x Driver quantity consumed by product / Units produced
Total unit cost under ABC = Direct materials + Direct labour + Sum of overhead from each cost pool
Gross margin
Gross margin % = (Selling price per unit - Unit cost) / Selling price per unit x 100
This is not a textbook-only problem. Any manufacturer that uses a single overhead rate and makes products of varying complexity will face cost distortion. Companies producing both standard high-volume goods and customised low-volume goods are especially vulnerable.
The shift from labour-based to activity-based allocation mirrors what happened across manufacturing in the 1980s and 1990s as automation reduced direct labour's share of total cost. When machines do most of the work and one worker runs several at once, labour hours stop being a meaningful proxy for resource consumption.
Students often think a high overhead rate (300%) means the company is inefficient. It does not. It means overhead is large relative to labour, which is normal in capital-intensive or automated environments. The problem is using labour as the allocation base, not the size of the rate.
Students sometimes assume that switching to ABC will always increase the cost of complex products and decrease the cost of simple ones. The direction depends on the specific cost drivers and volumes. ABC redistributes cost; it does not always move it in one predictable direction.
A common error is thinking that the "fix" is simply to lower the overhead rate. The rate is not the problem. The problem is that one rate is applied to products that consume overhead in fundamentally different patterns.
Students frequently confuse dropping a product with improving profitability. Dropping valves does not make their overhead disappear. That overhead would be reallocated to the remaining products unless the underlying costs are also eliminated.
⚠️ You will almost certainly be asked to compare product costs under the traditional system versus ABC. Be ready to calculate both and explain the difference.
⚠️ Know why labour-based allocation fails when workers run multiple machines. This is the central insight of the case.
⚠️ Expect a question on cost drivers. Be able to name the correct driver for each type of overhead (machine hours for machine costs, number of runs for set-up costs, number of shipments for shipping costs).
⚠️ Be prepared to discuss strategic implications: should Wilkerson drop a product, reprice, or shift its product mix? The answer depends on ABC data, not traditional cost data.
⚠️ Cross-subsidisation is a favourite exam topic. Under the traditional system, high-volume simple products subsidise low-volume complex products. Be able to explain this clearly.
True or False: Wilkerson's overhead allocation rate of 300% means the company has unusually high overhead compared to its industry.
Answer: False. The 300% rate simply reflects that overhead is large relative to direct labour. It says nothing about whether overhead is high or low compared to competitors.
Fill in the blank: Under Wilkerson's traditional system, overhead is allocated based on ______.
Answer: Production-run direct labour costs.
True or False: If one worker operates three machines simultaneously, labour hours and machine hours are the same.
Answer: False. One labour hour generates three machine hours in that scenario, which is exactly why machine hours are a better allocation base.
Fill in the blank: The cost of setting up a production run at Wilkerson is the same whether the run is ______ or ______.
Answer: Long or short (large batch or small batch).
True or False: Dropping a product line automatically eliminates the overhead that was allocated to it.
Answer: False. Unless the underlying costs (machines, staff, space) are also removed, the overhead remains and gets reallocated to the surviving products.
Q: Why is Wilkerson's traditional cost system likely to distort product costs?
A: The system allocates all overhead using a single rate (300% of direct labour), but the three products consume overhead resources in very different ways. Valves are high-volume with long production runs; flow controllers are low-volume with many set-ups and shipments. A single labour-based rate cannot capture these differences, so it over-costs simple products and under-costs complex ones.
Q: What cost drivers would an ABC system use for Wilkerson, and why?
A: Machine hours for machine-related overhead (because workers run multiple machines, so labour hours undercount machine usage), number of production runs for set-up costs (because each run requires a set-up regardless of batch size), and number of shipments for shipping and packaging costs (because the effort per shipment is constant regardless of volume shipped).
Q: Under ABC, which product's reported cost is most likely to increase, and why?
A: Flow controllers. They require more components, more labour, more machine time per unit, more production runs per unit (small batches), and more shipments per unit. Under the traditional system, they absorb less overhead than they actually cause because the labour-based rate does not reflect their disproportionate use of set-up and shipping resources.
Q: Should Wilkerson drop its valve product line? Explain your reasoning.
A: Not necessarily. Valves are likely over-costed under the traditional system, meaning their true margin may be higher than 35%. Dropping them would not eliminate the overhead currently allocated to them; it would shift to pumps and flow controllers. The better approach is to recalculate costs using ABC, then reprice or adjust the product mix based on accurate margins.
Q: Why are labour hours a poor basis for allocating overhead at Wilkerson?
A: Because workers operate multiple machines simultaneously. One hour of labour can correspond to several hours of machine time. Since much of the overhead is driven by machine usage, set-ups, and shipments rather than by how many hours a person works, labour hours fail to reflect the actual consumption of overhead resources.
This case connects directly to the broader topic of activity-based costing and activity-based management. If your course covers Cooper and Kaplan's ABC framework, Wilkerson is a worked application of those principles.
It also ties into product-mix and pricing decisions under constrained resources: once you have accurate costs, the next question is which products to emphasise, which to reprice, and which to reconsider.
If your course covers the theory of constraints or capacity analysis, note that Wilkerson's single-department structure means product-mix changes affect capacity utilisation across all three lines.
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