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The numbers behind it

Where the 30–40 % come from.

Every default in the calculator is tied to a published study. The combined figure is our model – not a measured customer result yet.

#What the study foundUsed forSource
1Rework consumes ~40 % of project effort; 70–85 % of that rework is caused by requirement errors.Rework share, requirement shareLeffingwell, Calculating the Return on Investment from More Effective Requirements Management, American Programmer 10(4), 1997 · Boehm & Basili, IEEE Computer 2001
2A requirement error costs 21–78× more to fix in integration & test and 29–1500× more in operation than when found in the requirements phase.Value of finding contradictions earlyStecklein et al., NASA JSC, Error Cost Escalation Through the Project Life Cycle, 2004
3Inadequate testing infrastructure costs the US economy $59.5 bn per year; finding and fixing defects accounts for ~80 % of development cost.Rework shareTassey, NIST Planning Report 02-3, 2002
4Verification is labour-intensive and may reach ~60 % of overall software development cost for dependable (DO-178C) systems.V&V share (default 40 %)Sun, Brain, Kroening et al., Functional Requirements-Based Automated Testing for Avionics, 2017
5Airbus replaced unit testing by formal "unit proof" on A380/A400M/A350 software; Dassault gained ~1 person-month per flight-software release by replacing robustness testing with Frama-C.Verification effort avoidedMoy, Ledinot, Delseny, Wiels, Monate, Testing or Formal Verification: DO-178C Alternatives and Industrial Experience, IEEE Software 2013
6Semi-automatic generation of test models from structured requirements saved 86 % of the time compared with manual creation, at equal quality.Verification effort avoidedFischbach et al., Automated Generation of Test Models from Semi-Structured Requirements, 2019
7EARS patterns, developed at Rolls-Royce for jet-engine control, gave qualitative and quantitative improvements over conventional text: less ambiguity, vagueness and omission. MBSE case studies with cost metrics attribute success mainly to defect prevention in requirements.Requirement defects avoidedMavin et al., EARS, IEEE RE'09 · Carroll & Malins, Sandia SAND2016-2607
8Generative AI: 56 % faster task completion in a controlled coding experiment; 14–15 % more output in a field study; but −19 % for experienced developers on their own large codebases. LLMs can generate Capella architectures and SysML v2 artefacts from requirements.AI authoring & modelling saving (default 35 %, deliberately below the coding figures)Peng et al. 2023 · Brynjolfsson, Li & Raymond, QJE 2025 · METR 2025 · LLM-generated Capella architectures, J. Eng. Design 2025
9Our model: 40 % × 35 % (verification) + 30 % × 70 % × 60 % (requirement rework) + 35 % × 35 % (AI authoring/modelling) ≈ 39 % of the engineering budget; conservative case ≈ 23 %.Headline figure 30–40 %EASY.SAFE – see calculator above; to be validated with pilot customers.