Citation indicators: PCI, PNCI and PCS

PCI — POSI Citation Impact

Citations to a journal’s citable items from a two-year publication window, per item, from OpenAlex (PCI-1.0; a five-year variant, PCI-5, is computed alongside). PCI is the source citation performance indicator. It is not normalized by field, so it is not compared across fields, and it does not decide a rank.

PCI is a Core Collection indicator: it is reported for Core Collection journals only. Indexed journals have no PCI; their citation performance is shown by PNCI and PCS.

PNCI — POSI Normalized Citation Indicator

PNCI = (1 / n) × Σ C_i / E(field_i, year_i, type_i)

Each eligible item’s citations are divided by the mean citations of all items of the same PSC field, publication year and document type, and the ratios are averaged over the journal’s items. 1.00 is the average of the comparison group. Because every item is compared with items like it, a large journal does not rank higher for its size, and older items do not outweigh recent ones (PNCI-1.0).

Citation Quartiles and POSI Zones are based on PNCI-derived percentiles within eligible PSC categories. See the ranking method.

PCS — POSI Citation Score

The mean Crossref citations of a journal’s citable items from the four complete years before the metric year (PCS-1.0): a view of citation performance independent of OpenAlex.

PCS is a supplementary citation indicator and does not determine the official POSI Citation Rank, Citation Percentile, Citation Quartile, or POSI Zone.

Reading the three together

• The three indicators are shown side by side and never averaged or used to correct one another.
• Total citations are shown as a description of a journal and never decide a rank.
• Citation indicators measure citation performance, not every dimension of scholarly quality.