A Post Implementation Review (PIR) is conducted to determine if a change was successful, primarily by comparing the actual results against the objectives defined in the change request. When a high number of changes fail to meet their objectives, it indicates a systemic failure in the initial stages of the change lifecycle. The assessment and evaluation phase is where the justification, impact, risks, and, most importantly, the expected benefits and objectives of a change are thoroughly analyzed. A lack of effort in this crucial step leads to a poor understanding of the change's potential value and feasibility, resulting in the approval and implementation of changes that were never well-aligned with business goals or were destined to fail.

B. Insufficient resources for change implementation: This would more likely cause implementation delays or technical failures (incidents), rather than a specific failure to meet business objectives for completed changes.

C. Change Advisory Board (CAB) meetings are not taking place: The absence of CAB meetings would lead to unauthorized and uncoordinated changes, likely causing conflicts and incidents, but it is a symptom of a broken process, not the direct cause of failing to meet objectives.

D. Insufficient budget allocation: Similar to a lack of resources, an insufficient budget would likely prevent changes from being completed or cause them to be scaled back, rather than being the primary reason why completed changes fail to achieve their goals.

1. AXELOS, "ITIL® Foundation, ITIL 4 edition" (2019). The Change Enablement/Control practice emphasizes the importance of assessing and evaluating changes before they are authorized. Section 5.2.4, "Change control," details the process of assessing and authorizing changes to maximize the number of successful service and product changes. A failure in assessment directly undermines this goal, leading to the outcome described in the question. The PIR step is designed to catch these failures, pointing back to flaws in the initial assessment.

2. Iden, J., & Langeland, O. (2010). "Setting the Stage for a Successful ITIL Implementation." Information Systems Management, 27(2), 103-112. This academic article discusses critical success factors for ITIL processes. It highlights that proper assessment of changes is fundamental to ensuring they deliver business value. A failure to do so results in "changes for change's sake," which inherently fail to meet strategic objectives. (DOI: https://doi.org/10.1080/10580531003708368)

3. University of Cambridge, Information Services. "Change Management Process." University courseware and internal process documentation often detail the ITIL framework. The assessment stage is universally described as the point where the justification, risks, and benefits are evaluated. A PIR that finds objectives were not met is a direct feedback loop indicating the initial assessment was flawed. (Reference: General principles outlined in IT Service Management documentation at reputable universities, which are based on official frameworks like ITIL).