文献计量指标可以通过比较特定的引文记录与参考文献集的数量来确定。然而，在计算引文数量时存在着一种模糊性，因为通常在百分位数等级之间的边界处会发现大量具有相同引用计数的论文。本案例研究的引用期刊欧洲物理学快报（EPL）在比较所有的物理论文从Web of Science显示的偏差，由于不同的方式来处理并列论文的高被引出版物的百分比的评估。如果被引用次数达到阈值的论文都被认为是高引用或都被认为不是高引用，则可能会出现强烈的偏倚。
英文摘要：
Bibliometric indicators can be determined by comparing specific citation records with the percentiles of a reference set. However, there exists an ambiguity in the computation of percentiles because usually a significant number of papers with the same citation count are found at the border between percentile rank classes. The present case study of the citations to the journal Europhysics Letters (EPL) in comparison with all physics papers from the Web of Science shows the deviations which occur due to the different ways of treating the tied papers in the evaluation of the percentage of highly cited publications. A strong bias can occur, if the papers tied at the threshold number of citations are all considered as highly cited or all considered as not highly cited.
Remaining problems with the "New Crown Indicator" (MNCS) of the CWTS
Waltman等人（2010年; arXiv：1003.2167）在其题为“Towards a new crown indicator：some theoretical considerations”的文章中指出，莱顿CWTS的“旧冠指标”在数学上不一致，应该采用“新冠指标”中应用的标准化。“尽管我们现在同意统计标准化，但“新冠指标”继承了“旧”指标的科学计量学问题，即把期刊的学科类别作为标准，对科学领域之间的引用行为差异进行标准化。我们进一步注意到，“平均值”不是测量偏态分布之间差异的适当统计量。在不改变“MNS”的缩写的情况下，可以定义“中位数标准化引文评分”。“这将使新冠指标与百分位数方法直接相关，例如，美国国家科学委员会的科学和工程指标（2010年）中使用的百分位数方法。根据定义，中位数等于第50百分位数。因此，该指标可以很容易地扩展为1%（=第99百分位）最高引用论文（Bornmann等人，印刷中）。必须使用非参数统计的表面上的缺点被可能的精度增益所补偿。
PP(top x%) is the proportion of papers of a unit (e.g. an institution or a group of researchers), which belongs to the x% most frequently cited papers in the corresponding fields and publication years. It has been proposed that x% of papers can be expected which belongs to the x% most frequently cited papers. In this Letter to the Editor we will present the results of an empirical test whether we can really have this expectation and how strong the deviations from the expected values are when many random samples are drawn from the database.
Bibliographic metrics are commonly utilized for evaluation purposes within academia, often in conjunction with other metrics. These metrics vary widely across fields and change with the seniority of the scholar; consequently, the only way to interpret these values is by comparison with other academics within the same field who are of similar seniority. Among the field- and time- normalized indicators, rank percentile has grown in popularity, and it is preferred over other types of indicators. In this paper, we propose and justify a novel rank percentile indicator for scholars. Furthermore, we …
The use of bibliometric indicators would simplify research assessments. The 2014 Research Excellence Framework (REF) is a peer review assessment of UK universities, whose results can be taken as benchmarks for bibliometric indicators. In this study we use the REF results to investigate whether the ep index and a top percentile of most cited papers could substitute for peer review. The probability that a random university's paper reaches a certain top percentile in the global distribution of papers is a power of the ep index, which can be calculated from the citation-based distribution of unive…
Which percentile-based approach should be preferred for calculating normalized citation impact values? An empirical comparison of five approaches including a newly developed citation-rank approach (P100)
Recently, the integrated impact indicator (I3) indicator was introduced where citations are weighted in accordance with the percentile rank class of each publication in a set of publications. I3 can also be used as a field-normalized indicator. Field-normalization is common practice in bibliometrics, especially when institutions and countries are compared. Publication and citation practices are so different among fields that citation impact is normalized for cross-field comparisons. In this study, we test the ability of the indicator to discriminate between quality levels of papers as defined …
The substantive and practical significance of citation impact differences between institutions: Guidelines for the analysis of percentiles using effect sizes and confidence intervals
In this paper, a new field-normalized indicator is introduced, which is rooted in early insights in bibliometrics, and is compared with several established field-normalized indicators (e.g. the mean normalized citation score, MNCS, and indicators based on percentile approaches). Garfield (1979) emphasizes that bare citation counts from different fields cannot be compared for evaluative purposes, because the "citation potential" can vary significantly between the fields. Garfield (1979) suggests that "the most accurate measure of citation potential is the average number of references per paper …
We combine the Integrated Impact Indicator (I3) and the h-index into the I3-type framework and introduce the publication vector X = (X1, X2, X3) and the citation vector Y = (Y1, Y2, Y3) , the publication score I3X=X1+X2+X3 and the citation score I3Y=Y1+Y2+Y3, and alternative indicators based on percentile classes generated by the h-index. These multivariate indicators can be used for academic evaluation. The empirical studies show that the h-core distribution is suitable to evaluate scholars, the X1 and Y1 are applied to measure core impact power of universities, and I3X and I3Y are alternativ…
How to improve the prediction based on citation impact percentiles for years shortly after the publication date?
Bornmann、Leydesdorff和Wang的研究结果表明，考虑期刊影响力可以提高对长期引文影响力的预测。本文进一步探讨了在短引文窗口的基础上，通过考虑期刊影响力和其他变量，如作者数、被引文献数和页数，改进引文影响力测量的可能性。该数据集包含1980年发表并在Web of Science（WoS，Thomson Reuters）中索引的475，391篇期刊论文，以及这些论文的所有年度引用计数（从1980年到2010年）。作为引文影响力的指标，我们使用了使用Hazen（1914）方法计算的引文数量。我们的研究结果表明，引文影响测量确实可以改进：如果在统计分析中考虑影响引文影响的一般因素，长期引文影响的解释方差可以大大增加。然而，这种增长只有在使用出版后不久的年份时才能看到，而在使用以后的年份时则看不到。
In December 2016, after several years of development, Elsevier launched a set of transparent, comprehensive, current, and freely-available journal citation metrics called CiteScore metrics. Most of the CiteScore metrics are static, annual indicators calculated from the dynamic Scopus citation index. In the spirit of recent public statements on the responsible use of metrics, we outline the desirable characteristics of journal citation metrics, discuss how we decided on the cited and citing publications years and document types to be used for CiteScore metrics, and detail the precise method of …
This article analyses the difference in timing between the online availability of articles and their corresponding print publication and how it affects two bibliometric indicators: Journal Impact Factor (JIF) and Immediacy Index. This research examined 18,526 articles, the complete collection of articles and reviews published by a set of 61 journals on Urology and Nephrology in 2013 and 2014. The findings suggest that Advance Online Publication (AOP) accelerates the citation of articles and affects the JIF and Immediacy Index values. Regarding the JIF values, the comparison between journals wi…
The top 1 percent most highly cited articles are watched closely as the vanguards of the sciences. Using Web of Science data, one can find that China had overtaken the USA in the relative participation in the top 1 percent in 2019, after outcompeting the EU on this indicator in 2015. However, this finding contrasts with repeated reports of Western agencies that the quality of Chinese output in science is lagging other advanced nations, even as it has caught up in numbers of articles. The difference between the results presented here and the previous results depends mainly upon field normalizat…
