# How Traditional Costing Methods Hinder the Development of Modular Product Architectures
## 2 Research Methods
### Literature Study Process  
The literature search, inspired by the approach of [PERSON] et al. [21] and [PERSON] et al. [22], was based on a continuously updated list of relevant keywords identified throughout the process. The first set of keywords relied on previous publications in the field [5; 18; 23]. However, combining keywords from the research fields of Management Accounting and Design Research would yield dispersed results due to the use of different terminology inherent to each research topic. Therefore, the search strategy was made to include two separate search strings with their own unique set of keywords. The combination of these keywords formed two extensive search strings, specifically targeting each area of research (strings listed below). They were submitted to the scientific databases Scopus and Web of Science, which were deemed appropriate for this review, since Scopus is one of the major scientific databases [24], and both databases are multidisciplinary bibliographic data sources [25]. Additional material was found through the citation and reference-tracing features, which are available within these databases. The papers found in each of the two searches were first manually screened by title to identify relevant work, and then the selection was further narrowed by assessing the abstracts. The remaining papers were thoroughly reviewed before determining their relevance to this study. This procedure allowed for the exclusion of non-relevant articles or duplicates.  
1. TITLE-ABS-KEY (\"complexity management\" OR \"complexity costs\" OR \"quantification of complexity costs\" OR \"complexity reduction\" OR \"External Product Vari\" OR \"Indirect Cost\" OR \"variant management\" OR \"variant cost\") AND TITLE-ABS-KEY (\"product architecture\" OR \"modular\" OR \"data management\" OR \"MBSE\" OR \"SysML\" OR \"KPIs\" OR \"decision support\" OR \"product concept evaluation\" OR \"knowledge management\" OR \" design knowledge\")
2. TITLE-ABS-KEY (\"Cost systems\" OR \"External Product Vari\" OR \"variant cost\" OR \"Activity-Based cost\" OR \"ABC\" OR \"Cost Accounting\" OR \"Cost Allocation\") AND TITLE-ABS-KEY (\"product architecture\" OR \"modular\")  
The purpose of the search strings was to collect all the existing and accessible material addressing the cost of product variance and its relation to modular product architectures. And more specifically, how it is affected by current cost allocation practices and methods.  
The relevance of the studies included in the final selection was ensured through the application of the following inclusion criteria in the literature review: The retrieved studies should (1) be within the Engineering, Management, and/or Accounting fields. (2) English texts only. (3) Adhering to the purpose of the review as stated above.  
The first string found 384 papers with duplicates. The screening for titles reduced the number to 78, and a further reduction to 19 studies was made through the screening of abstracts. Reading the remaining papers revealed that only 10 papers had a relevant scope regarding the assessment of economic benefits when developing modular product architectures, and three of these were highly relevant to this study. The second search string, following the same procedure, reduced the total number of papers from 606 to 19 and 8 after the title and abstract screening, respectively. Upon reviewing the full text, four additional papers were identified as highly relevant to this study by addressing the limitations of current costing methods in allocating costs for a modular product architecture. The final set of included studies spans from 2006 to 2024, with the majority of papers published in the last decade. This study does not claim to cover all papers investigating the gap between MA and IOM research on the topic of the economic benefits of modularization and costing methods across the product LCPs. However, a significant portion of the papers on this specific topic are believed to be covered in this review.