1. Flaws of Traditional Volume-Based Overhead Allocation
Traditional costing structures allocate overhead using single, company-wide plant rates or departmental rates tied directly to high-volume metrics (like direct labor or machine hours). In modern, automated production ecosystems, this leads to product cost distortion:
  • High-volume, simple products are over-costed because they consume more labor hours, artificially absorbing unrelated overhead.
  • Low-volume, complex, highly customized products are under-costed because they consume fewer labor hours but require extensive engineering set-ups and testing processes.

2. The Mechanics of Activity-Based Costing (ABC)
ABC improves costing accuracy by tracking overhead consumption down to specific operational activities. It allocates costs using a two-stage process:
  Stage 1: Resource Costs ──► Assigned to Activity Cost Pools (e.g., Machine Setups)
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  Stage 2: Activity Pools ──► Allocated to Products using Activity Cost Drivers

3. ABC Hierarchy of Activities
To organize cost pools effectively, ABC groups organizational activities into four key management tiers:
  • Unit-Level Activities: Performed each time a single unit is produced (e.g., machine electricity).
  • Batch-Level Activities: Performed each time a batch of goods is processed, regardless of size (e.g., machine setups, shipment staging).
  • Product-Level Activities: Performed to support an entire specific product line (e.g., product design changes, parts engineering).
  • Facility-Sustaining Activities: Performed to maintain the overall production facility (e.g., factory security, heating, factory manager salary).

 
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