Crown Indicator (CPP/FCSm)
Also known as: CPP/FCSm, old crown indicator, Leiden crown indicator, CWTS crown indicator
The crown indicator, written CPP/FCSm, was the field-normalized citation impact measure developed at the Centre for Science and Technology Studies (CWTS) in Leiden and described by Moed, De Bruin, and Van Leeuwen in 1995. It compares a unit's observed citation rate with what would be expected given the fields, document types, and years in which it published. Specifically, it divides the citations per publication (CPP) by the mean field citation score (FCSm), forming a ratio in which a value of 1 marks performance exactly at the field average. For more than a decade it was CWTS's flagship indicator, until Waltman and colleagues showed in 2011 that its ratio-of-averages construction had statistical drawbacks and proposed the MNCS as a successor.
Key highlights
- Normalizes citation impact by field, document type, and year, enabling cross-disciplinary comparison.
- Anchored at an interpretable benchmark of 1, marking performance at the field average.
- Long-established CWTS standard with an extensive track record in institutional and national evaluation.
- Conceptually simple as a ratio of observed to expected citations for a whole unit.
Intuition
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How it works
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When to use it
The crown indicator is appropriate when you need a field-normalized citation impact measure for evaluating and ranking research units across disciplines, and it remains useful for understanding the historical CWTS methodology and for reproducing older Leiden assessments. For new evaluations the average-of-ratios MNCS is generally preferred, because the crown indicator's ratio-of-averages form lets high-citation fields dominate. Use CPP/FCSm when continuity with prior crown-indicator studies is required or when its specific aggregation is desired, but disclose the field-classification scheme, and avoid it for small publication sets where averages are unstable or for fine-grained comparison where the field-weighting bias matters.
Strengths & limitations
- Normalizes citation impact by field, document type, and year, enabling cross-disciplinary comparison.
- Anchored at an interpretable benchmark of 1, marking performance at the field average.
- Long-established CWTS standard with an extensive track record in institutional and national evaluation.
- Conceptually simple as a ratio of observed to expected citations for a whole unit.
- Its ratio-of-averages construction implicitly weights fields by citation density, biasing results toward high-citation fields.
- Shown by Waltman et al. (2011) to have inconsistent statistical properties, prompting its replacement by the MNCS.
- Sensitive to the field-classification scheme used to compute expected citations.
- Unstable for small publication sets, where a few papers can swing the averages.
Common pitfalls
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Applications
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Frequently asked
What does the crown indicator CPP/FCSm measure?
It measures a research unit's citation impact relative to the world norm for its fields. The numerator CPP is the unit's average citations per publication, and the denominator FCSm is the average citation rate expected for papers of the same field, type, and year. Their ratio equals 1 when the unit is cited exactly at the field average, above 1 when it outperforms, and below 1 when it underperforms, making impact comparable across disciplines.
Why was the crown indicator replaced by the MNCS?
The crown indicator divides total observed citations by total expected citations, a ratio of averages. Waltman and colleagues showed in 2011 that this lets fields with high citation densities dominate the result and gives the indicator inconsistent statistical properties. The MNCS instead averages the per-paper normalized scores, an average of ratios, so every publication counts equally. Because of these advantages the MNCS became the new crown indicator at CWTS.
Is the crown indicator still useful today?
Yes, chiefly for understanding and reproducing the historical CWTS methodology and for continuity with earlier evaluations. For new assessments the MNCS is preferred because of its better statistical behavior. When the crown indicator is used, the field-classification scheme should be disclosed, small samples avoided, and results not compared across incompatible classifications or databases.
Sources
- 1.Moed, H. F., De Bruin, R. E., & Van Leeuwen, T. N. (1995). New bibliometric tools for the assessment of national research performance: Database description, overview of indicators and first applications. Scientometrics, 33(3), 381-422.
- 2.Waltman, L., van Eck, N. J., van Leeuwen, T. N., Visser, M. S., & van Raan, A. F. J. (2011). Towards a new crown indicator: Some theoretical considerations. Journal of Informetrics, 5(1), 37-47.
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Cite this page
ScholarGate. (2026, June 23). Crown Indicator (CPP/FCSm). ScholarGate. https://scholargate.app/bibliometrics/crown-indicator-cpp-fcsm