How Traditional Costing Systems Can Lead to Distortions

When a business allocates costs inaccurately, every decision built on those numbers – pricing, profitability analysis, product mix – becomes unreliable. This is exactly what happens with traditional costing systems. Designed for a simpler era of manufacturing, these systems use a single cost driver to spread overhead across all products, regardless of how differently those products actually consume resources. The result: some products are charged too much, others too little, and the whole picture becomes distorted.

What traditional costing systems actually do 🔗

Traditional costing allocates factory overhead to products based on the volume of production resources consumed. In practice, this means choosing one measure – typically direct labor hours or machine hours – and using it as the single basis for distributing all overhead costs across every product a business makes.

This approach made sense in the early 20th century, when direct labor dominated total costs and overhead was relatively small. But modern production environments look very different. Overhead costs today often include quality inspections, machine setups, procurement, regulatory compliance, and customer-specific handling – none of which necessarily scale with labor hours or machine time. Applying a single cost driver to such a varied mix of costs creates an incomplete and often misleading picture of what it actually costs to make each product.

How distortions occur 🔗

The core problem is an assumption that all products consume overhead in proportion to the chosen cost driver. This approach assumes all overhead costs are proportional to the chosen cost driver, which is often not true. In reality, different products make very different demands on a company’s resources – and a single allocation base simply cannot capture that variation.

Consider two products on the same production floor: a standard high-volume item that runs continuously with minimal interruption, and a low-volume specialized product that requires engineering reviews, custom setups, and additional quality checks. Under a traditional system using machine hours, the high-volume product absorbs the bulk of overhead – because it logs more hours – even though the specialized product is actually driving more of the indirect costs. The high-volume product gets overcosted; the specialized one gets undercosted. Neither figure reflects reality.

Over-costing and under-costing 🔗

These two outcomes – over-costing and under-costing – are the most direct consequences of relying on a single allocation base. Products with high production volumes often get allocated more overhead than they actually consume, making them appear more expensive than they are. Conversely, low-volume or complex products may consume more overhead but are allocated less, leading to under-costing.

This imbalance is particularly problematic in businesses with a diverse product range. As AccountingCoach explains, the more diverse a company’s products and customer requirements, the bigger the gap between actual resource consumption and the amounts assigned through a single cost driver. A special customer order requiring significant handling and coordination might be assigned very little overhead simply because it uses few machine hours – even though it places substantial demands on indirect resources.

Product cost cross-subsidization 🔗

A closely related distortion is product cost cross-subsidization. This occurs when overcosted high-volume products effectively subsidize undercosted low-volume or complex ones. The high-volume products appear less profitable than they truly are, while complex products look more profitable. Managers relying on these figures may inadvertently push resources toward products that are actually loss-making, while scaling back on genuinely profitable lines.

As illustrated in management accounting research, if one product is produced in far greater quantities than another, a traditional system assigns it a proportionally larger share of overhead – even for cost categories like setup and batch processing, which are driven by the number of production runs, not the number of units. A high-volume product requiring 10 times more units gets allocated 10 times more setup costs, regardless of whether it actually uses more setups. That is a clear misallocation.

The downstream impact on business decisions 🔗

Distorted costs do not stay on the balance sheet – they flow directly into decisions.

Pricing errors 🔗

When a product’s cost is overstated, a company may set its price too high and lose business to competitors. When a cost is understated, a product may be priced below what it actually costs to produce, quietly eroding margins. The distorted overhead allocations resulting from a traditional costing system make it difficult to set competitive and profitable pricing. In competitive markets, this can be the difference between winning and losing contracts – or between sustainable margins and undetected losses.

Flawed profitability analysis 🔗

Managers use product cost data to evaluate which items in the portfolio are worth keeping, expanding, or discontinuing. If costs are systematically distorted, these evaluations lead to wrong conclusions. A product that appears profitable under traditional costing may actually be generating a loss once its true resource consumption is properly accounted for. ABC showed that the Solo product creates a loss for the company in a widely cited teaching example – something the traditional costing method had completely obscured.

Strategic missteps 🔗

Beyond pricing and profitability, distorted costs can affect broader strategic choices: which markets to enter, which customers to pursue, whether to outsource, and how to allocate capital. Decisions made on inaccurate cost data carry compounding risk – each one building on a flawed foundation.

When traditional costing still works 🔗

It is worth noting that traditional costing is not without value. It remains useful for external financial reporting, where the goal is simply to value ending inventory and calculate the cost of goods sold. It is also adequate for businesses with a homogeneous product mix, where all products make similar demands on resources and direct labor genuinely drives overhead. When direct labor is a large portion of the product cost, the overhead costs tend to be consistently driven by one cost driver, and the traditional method appropriately allocates those costs.

The problems emerge when product diversity increases, overhead grows as a share of total costs, and production processes become more complex. In those conditions, a single cost driver becomes an increasingly poor proxy for actual resource use.

How Activity-Based Costing addresses these distortions 🔗

Activity-Based Costing (ABC) was developed specifically to overcome the limitations of single-driver allocation. Rather than pooling all overhead and distributing it through one measure, ABC first assigns costs to the activities that are the real cause of the overhead, then assigns the cost of those activities only to the products that are actually demanding them.

Instead of one overhead rate, ABC uses multiple cost pools – each tied to a specific activity such as machine setup, quality inspection, procurement, or order processing. Each pool has its own cost driver that reflects what actually causes that cost to be incurred. A product requiring 10 setups is assigned 10 setups’ worth of cost; one requiring 2 is assigned 2. The allocation follows actual consumption, not volume proxies.

A practical illustration 🔗

Consider a real-world example from CliffsNotes accounting resources: a manufacturer producing both hollow-center and solid-center balls. Under traditional costing using direct labor dollars, the solid-center ball – with higher labor input – is allocated $0.53 per unit in overhead. Under ABC, which accounts for actual activity consumption, the true figure is just $0.44. Conversely, the hollow-center ball, which consumes more support activities relative to its labor cost, is assigned $0.35 under traditional costing but $0.52 under ABC. The swing in both directions has direct implications for pricing and margin management.

Multiple cost drivers, more accurate costs 🔗

The use of a single cost driver may overallocate overhead to one product and underallocate overhead to another, resulting in erroneous total costs and potentially setting an incorrect sales price. ABC resolves this by matching each category of overhead to the activity that causes it – giving managers a much clearer view of which products, customers, or processes are genuinely profitable.

It is also worth noting that ABC is not without trade-offs. It requires more data collection, more analysis, and more resources to implement and maintain. For smaller organizations with simple product lines, the added complexity may outweigh the benefits. But for businesses where overhead is substantial and products vary significantly in complexity, ABC systems are more accurate than traditional costing systems, providing a more precise breakdown of indirect costs.

Recognizing the warning signs 🔗

Several indicators suggest that a traditional costing system may be producing unreliable data. If product profitability shifts dramatically with small changes in volume, if managers struggle to explain why certain products or customers appear more or less profitable, or if overhead has grown significantly as a share of total costs, these are signals worth taking seriously. Similarly, if a company’s product range has expanded or diversified over time, the single-driver model becomes progressively less representative of actual cost behavior.

The goal of any costing system is to give decision-makers an accurate picture of where money is being spent and why. Traditional costing was a practical solution for its time. But as production environments have grown more complex, the gaps it leaves have grown with them – and those gaps, left unaddressed, translate directly into poor decisions.

What do you think? If your business produces a mix of high-volume standard products and low-volume specialized ones, how confident are you that your current costing system reflects the true cost of each? And given that implementing ABC requires significant data and effort, how would you decide at what point the accuracy gain justifies the added complexity?

References

1. https://www.accountingtools.com/articles/what-is-traditional-costing.html
2. https://www.accountingcoach.com/blog/traditional-method-allocating-overhead
3. https://maaw.info/Chapter7.htm
4. https://openstax.org/books/principles-managerial-accounting/pages/6-4-compare-and-contrast-traditional-and-activity-based-costing-systems
5. https://psu.pb.unizin.org/acctg211/chapter/comparing-traditional-activity-based-costing/
6. https://www.accountingcoach.com/activity-based-costing/explanation
7. https://www.cliffsnotes.com/study-guides/accounting/accounting-principles-ii/activity-based-costing/activity-based-vs-traditional-costing
8. https://biz.libretexts.org/Bookshelves/Accounting/Managerial_Accounting_(OpenStax)/06:_Activity-Based_Variable_and_Absorption_Costing/6.05:_Compare_and_Contrast_Traditional_and_Activity-Based_Costing_Systems
9. https://strategiccfo.com/articles/banking-financing/activity-based-costing-abc-vs-traditional-costing/