19. Citation Analysis and Databases

Academic databases serve as massive repositories of research information, primarily tracking how often published works are referenced by other scholars. This is known as Citation Analysis, and it is the primary way the scientific community evaluates the importance and quality of both journals and individual researchers.

Major Academic Citation Databases

• Web of Science (WoS): Features multiple citation indexes (Science Citation Index, Social Sciences Citation Index, Emerging Sources Citation Index). Journals under WoS are heavily vetted for quality.
• Scopus: An Elsevier database covering peer-reviewed journals. It provides citation info and quality metrics like CiteScore, SJR, and SNIP.
• Google Scholar: A freely accessible search engine that tracks citations accurately but draws from a much broader and sometimes less-vetted pool than WoS or Scopus.

Evaluating Journal Quality (Impact Factors)

Journals are rated by evaluating how frequently their articles are cited by the global research community.

1. Journal Impact Factor (JIF): Managed by Clarivate Analytics (Web of Science). It calculates the average number of citations received in a given year by articles published in that journal during the two preceding years. Highly prestigious journals have a high JIF.

- Formula: \text{JIF}_{2020} = \frac{\text{Citations in 2020 to articles published in 2018 and 2019}}{\text{Total citable items published in 2018 and 2019}}

1. CiteScore: Elsevier’s (Scopus) alternative measure to the JIF. It computes the average citations received over a three-year period rather than two.

- Formula: \text{CiteScore}_{2020} = \frac{\text{Citations in 2020 to articles published in 2017, 2018, and 2019}}{\text{Total citable items published in 2017, 2018, and 2019}}

1. SCImago Journal Rank (SJR): Weighs citations based on the prestige of the journals they come from (a citation from a highly respected journal counts for more).
2. Source Normalized Impact Per Paper (SNIP): Contextualizes citations depending on the specific subject field to allow for fair comparisons between different disciplines (e.g., medical papers get cited far more frequently than pure mathematics papers).

Evaluating Author Quality

Evaluating a journal doesn't always reflect an individual author's specific contribution. Author impact metrics fill this gap:

• h-index: Proposed by Jorge E. Hirsch. An author has an index of h if h of their papers have been cited at least h times. (e.g., an h-index of 6 means the author has 6 papers that have each received at least 6 citations). It measures both productivity and citation impact simultaneously.

- Formula Condition: Maximize h such that \text{citations of the } h\text{-th most cited paper} \ge h.

• i10-Index: Created by Google Scholar. It simply represents the total number of publications an author has that have at least 10 citations.
• g-index: Similar to the h-index but places more weight and mathematical value on an author's most highly cited breakthrough papers.

- Formula Condition: Given a set of articles ranked in decreasing order of citations, the g-index is the largest number g such that the top g articles received (together) at least g^2 citations.

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