Journal Citation Reports: Understanding Rank Proportions, Quartile Boundaries, and the 2025 Retraction Citation Policy

Purpose: Journal Citation Reports (JCR) from Clarivate provides annual rankings of scholarly journals through Journal Impact Factor (JIF) quartiles and percentiles. These metrics are widely used in research evaluation, funding decisions, and academic promotion across all scientific disciplines. Despite their institutional significance, persistent misunderstandings remain regarding the precise mathematical derivation of quartile boundaries, the distinction between rank proportion and percentile measures, and the implications of the June 2025 policy reform that excludes retracted citations from JIF numerators—a fundamental methodological change that has not yet been systematically analyzed in the scientometrics literature. This study addresses these gaps by providing the first consolidated methodological synthesis of JCR quartile mathematics, systematically distinguishing between quartile classification and JIF Percentile calculation, and presenting the first detailed analysis of the 2025 retraction citation exclusion policy. Methods: A documentary research design was employed, comprising systematic collection, critical evaluation, and synthetic analysis of primary and secondary sources. Primary sources comprised official Clarivate technical documentation accessed through the Clarivate Scientific and Academic Research support portal in March 2025, including the definitive specification of quartile and percentile calculation methodologies. Secondary sources comprised five institutional research guides from major universities, peer-reviewed editorial commentary, independent bibliometric analysis, and foundational scientometrics literature. Analytical procedures proceeded in three stages: (1) extraction and verification of the rank proportion formula (Z = X/Y) and quartile boundary definitions; (2) extraction and verification of the JIF Percentile formula (N – R + 0.5)/N × 100 and analysis of its mathematical relationship to quartile classification; and (3) synthesis of policy specifications, rationale, estimated effects, and potential implications of the 2025 integrity reform. Findings: Three principal findings emerge. First, JCR quartile assignment follows a precise mathematical specification with rank proportion (Z = X/Y) and strict boundary definitions invariant across all subject categories and publication years: Q1 (0.0 < Z ≤ 0.25), Q2 (0.25 < Z ≤ 0.5), Q3 (0.5 < Z ≤ 0.75), and Q4 (0.75 < Z). Borderline cases at Z = 0.25 and Z = 0.50 are explicitly classified as Q1 and Q2 respectively. Derived quantile rankings—terciles, quintiles, and deciles—can be mathematically consistently generated using the identical rank proportion convention, although these are not officially published or endorsed by Clarivate. Second, JIF Percentile provides granular, cross-categorically comparable information that quartile classification necessarily discards. The formula (N – R + 0.5)/N × 100 transforms discrete rank positions into a continuous 0–100 distribution. Because rank proportion (Z) increases with descending rank position, quartile boundaries inversely correspond to percentile thresholds. Third, the June 2025 Clarivate policy excludes citations to and from retracted articles from JIF numerators while retaining retracted articles in denominators. This represents the first formal encoding of integrity considerations into JIF methodology. The policy applies exclusively to JIF calculation and does not affect CiteScore, h-index, or other researcher-level metrics. Approximately 1% of JCR-indexed journals are expected to experience measurable JIF changes with minimal anticipated rank displacement. A potential unintended consequence—that increasing the negative JIF impact of retractions may inadvertently disincentivize retractions—is balanced against Clarivate's stated position that failure to retract compromised content risks journal delisting. Conclusion: This study provides the first methodological synthesis in the peer-reviewed scientometrics literature of JCR quartile mathematics, JIF Percentile calculation, and the 2025 integrity reform. Quartile assignment follows a precise rank proportion specification (Z = X/Y) that can be explicitly articulated and applied across all category sizes. JIF Percentile provides continuous cross-categorically comparable information that quartile classification necessarily discards; researchers and evaluators should consult percentiles, not merely quartiles, when fine-grained differentiation is required. The 2025 integrity reform represents one of the most consequential methodological changes in the Journal Impact Factor's history, formally acknowledging that how citations are accumulated matters as much as how many. This work provides researchers, evaluators, librarians, and bibliometricians with an authoritative technical reference for understanding both established JCR metrics and transformative policy changes.