Methodology
How POSI evaluates journals: Core Collection eligibility, lifecycle ratings, citation indicators, and the subject-level Citation Ranking with its quartiles and zones. Formulas, thresholds and versions are published here; journal pages show results only.
1. POSI Evaluation Architecture
POSI evaluates a journal in five separate layers (POSI-EVAL-1.0). Each answers one question and has its own vocabulary; no layer feeds or relabels another.
| Layer | Question | Published as |
|---|---|---|
| PQF | Can the journal enter, or remain in, the Core Collection? | Score 0–100 and an eligibility status |
| AJR | How strong is the journal’s lifecycle and publishing-development profile? | AJR Score 0–100 and AJR Rating A+ to D |
| PCI, PNCI, PCS | What does citation evidence show? | Citation indicators |
| Citation Ranking | Where does the journal rank within its PSC category? | Citation Rank, Citation Percentile, Citation Quartile C-Q1 to C-Q4, from PNCI |
| POSI Zones | POSI’s selective grouping of the same ranking | Zone 1 to Zone 4, from the same percentile |
PQF is not a ranking. AJR is not a quartile. PCS does not decide any rank. PNCI is the metric of the official subject rankings; the Citation Quartile is the standard 25-point grouping of its percentile, and the POSI Zone a selective grouping of the same percentile. Q1–Q4 are used for the Citation Quartile only, shown as C-Q1 to C-Q4.
2. Core Collection Eligibility — PQF
The POSI Quality Framework scores six factors from 100 points (transparency, metadata quality, editorial governance, technical discoverability, citation visibility, research integrity; see the PQF page and the editorial policy). Its result is an eligibility status:
| PQF score | Status |
|---|---|
| ≥ 70 | Eligible |
| 50–69.99 | Review Required |
| 40–49.99 | Insufficient Evidence |
| < 40 | Not Eligible |
PQF is an eligibility and quality-framework assessment. It is not a citation ranking metric and does not determine Citation Quartiles or POSI Zones. PQF may be used as a filter (for example PQF ≥ 70); it is never a sort order for journals.
3. Journal Lifecycle Evaluation — AJR
AJR evaluates a journal by lifecycle stage, counted in months since its first publication. It is published for Core Collection journals only; other journals show no AJR.
- Observation, 0–11 months: too early to rate; no score.
- AJR-E (Early-stage Journal Rating), 12–59 months.
- AJR-M (Mature Journal Rating), 60 months or more.
Each model gives an AJR Score from 0 to 100 and an AJR Rating:
| AJR Score | AJR Rating |
|---|---|
| 90.00–100.00 | A+ |
| 85.00–89.99 | A |
| 80.00–84.99 | A− |
| 75.00–79.99 | B+ |
| 70.00–74.99 | B |
| 65.00–69.99 | B− |
| 60.00–64.99 | C+ |
| 50.00–59.99 | C |
| 0.00–49.99 | D |
AJR Ratings are absolute lifecycle ratings. They are not citation quartiles and should not be interpreted as relative subject rankings. The rating is read from the score alone. Earlier E-Q and M-Q quartiles are withdrawn and are never converted into ratings. See AJR ratings.
4. Citation Indicators
PCI — POSI Citation Impact
The source citation performance indicator: citations to a journal’s citable items from a two-year publication window, per item, from OpenAlex (PCI-1.0). PCI is not normalized by field and is not compared across fields. PCI is a Core Collection indicator: it is reported for Core Collection journals only, and indexed journals have none.
PNCI — POSI Normalized Citation Indicator
The primary ranking metric. Each eligible item’s citations are divided by the expected citations of items like it:
PNCI = (1 / n) × Σ Ci / E(fieldi, yeari, typei)
- Ci: citations to item i; n: the journal’s eligible items.
- E: the mean citations of all eligible items of the same PSC field, publication year and document type. Where that group has fewer than 50 items, the field and publication year are used.
- 1.00 is the average of the comparison group; above 1 is above it, below 1 below it.
- Items: the citable items of the four complete years before the metric year, with Crossref citation counts (
PNCI-1.0).
PCS — POSI Citation Score
A supplementary independent citation indicator: the mean Crossref citations of a journal’s citable items from the four complete years before the metric year (for 2026: 2022 to 2025), PCS-1.0. PCS is a supplementary citation indicator and does not determine the official POSI Citation Rank, Citation Percentile, Citation Quartile, or POSI Zone.
PCI, PNCI and PCS are shown side by side and are never averaged. Total citations are descriptive and never decide a rank. More on each indicator on the citation indicators page.
5. Citation Ranking Method
Citation Quartiles and POSI Zones are based on PNCI-derived percentiles within eligible PSC categories.
- The cohort is the journals of one PSC category that meet the minimum data requirements (§ 9). Categories are never pooled.
- Journals are ordered by PNCI, highest first, on unrounded values.
- The Citation Rank is the position in that order; tied journals share it (§ 10).
6. Citation Percentiles
For a group of tied journals occupying positions rstart to rend in a cohort of N:
rmid = (rstart + rend) / 2 percentile = 100 × (N − rmid + 0.5) / N
Percentiles are stored at full precision, limited to 0–100, and shown with one decimal.
7. Citation Quartiles
| Percentile | Citation Quartile |
|---|---|
| ≥ 75 | C-Q1 |
| 50 to < 75 | C-Q2 |
| 25 to < 50 | C-Q3 |
| < 25 | C-Q4 |
The C stands for Citation, so that POSI quartiles are not confused with those of other services. Quartiles follow the percentile, so they do not always hold exactly 25% of a category.
8. POSI Zones
POSI Zones (POSI 分区) read the same percentile, counted from the top of the ranking:
| Percentile | Zone | Share of the ranking |
|---|---|---|
| ≥ 95 | Zone 1 · Top 5% | Top 5% |
| 80 to < 95 | Zone 2 · Top 5–20% | 5th–20th percentile from the top |
| 50 to < 80 | Zone 3 · Top 20–50% | 20th–50th percentile from the top |
| < 50 | Zone 4 · Top 50–100% | Lower 50% |
Zones are independent of the quartile: a C-Q1 journal can be in Zone 1, 2 or 3. Official zones need a category of at least 50 ranked journals (§ 9). Rule POSI-ZONES-2.0; the earlier PCS-based trial (POSI-ZONES-1.0) is withdrawn.
9. Minimum Data Requirements
| Requirement | Official | Otherwise |
|---|---|---|
| Eligible citable items | 20 or more, from at least 2 publication years | 10–19 items or a single year: provisional. Fewer than 10: insufficient data (observation period for journals under 12 months) |
| Citation coverage | Citation data retrieved for at least 90% of eligible items | Incomplete citation coverage: not ranked |
| PSC category | High-confidence or editor-confirmed, not multidisciplinary | PNCI shown, not ranked |
What a category publishes depends on its number of ranked journals, N:
| N | Rank, percentile, Citation Quartile | POSI Zone |
|---|---|---|
| ≥ 50 | Yes | Official |
| 30–49 | Yes | Provisional |
| 20–29 | Yes | None |
| < 20 | No (PNCI only): Insufficient Category Size | None |
A journal’s age does not decide its Citation Ranking: a young journal is ranked once it meets these requirements, and its lifecycle stage is shown beside it.
10. Ties
Journals with the same PNCI share the same rank (1, 2, 2, 4), the same mid-rank percentile, and therefore the same quartile and zone. Ties are never broken by title, ISSN, date or record id.
11. Provisional Rankings
A provisional ranking (10–19 eligible items, or items from a single publication year) has a rank, percentile and quartile marked “Provisional” (for example Provisional C-Q2) and no zone. Provisional journals keep their place in the category, so the percentiles of official journals do not depend on whether they are shown.
12. Category Assignment
Each journal is assigned one primary category of the POSI Subject Classification (PSC): 42 categories in six domains, computed from the journal’s OpenAlex topics through a fixed crosswalk.
| Assignment | Rule | Ranked |
|---|---|---|
| High confidence | The leading category holds at least 35% of the journal’s topic mass, at least 1.5 times the next category, and the journal has at least 50 works. | Yes |
| Provisional | A category leads, but on fewer than 50 works, or without a clear margin. | No |
| Multidisciplinary | No category and no domain dominates. | No |
| Not classified | No topic data. | No |
An editor-confirmed primary category takes precedence. Confirmation records whether the classification is correct; it never moves a journal to the category where its quartile would be better.
13. Ranking Snapshots
The journal index is built from Crossref and OpenAlex, merged on ISSN, and refreshed daily. Citations are harvested in cycles; each cycle computes PCS and PNCI for every indexed journal and publishes a Citation Ranking edition with its snapshot date. Every rank states the snapshot and model that produced it; a published edition is never recomputed in place. Current snapshot: September 2026 (2026-09-28).
14. Versioning
| Evaluation architecture | POSI-EVAL-1.0 |
| Citation ranking | CITATION-RANK-1.0 |
| PNCI | PNCI-1.0 |
| POSI Zones | POSI-ZONES-2.0 |
| AJR | AJR-E-1.2, AJR-M-1.2 and Evidence Coverage EC-1.1 from the October 2026 rerate (earlier ratings: AJR-E-1.1; no AJR-M rating was published before), rating scale AJR-RATING-1.0 |
| PQF | PQF v1.0 |
| PCI, PCS | PCI-1.0, PCS-1.0 |
| Subject crosswalk | PSC-CROSSWALK-0.3 |
A change to any formula or threshold is a new version, announced in news. Retired: the PCS-based quartiles (PCS-Q), the lifecycle quartiles (E-Q, M-Q) and the PCI-based Citation Q. For sources and verification see provenance.
15. Limitations
- Citation indicators measure citation performance, not every dimension of scholarly quality.
- Citation practices vary across fields.
- PNCI reduces but cannot eliminate all disciplinary and database-coverage differences.
- New or small journals may have unstable estimates. POSI therefore applies minimum sample, coverage, and category-size requirements.
- A ranking describes a journal in one snapshot. It does not assess individual articles or researchers; see responsible use.