Q: What types of data is featured in Essential Science Indicators?
A: Types of data featured in Essential Science Indicators include most cited scientist rankings, institutional (university, corporate, government research lab) rankings, country rankings, and journal rankings. Rankings are broken out by field as well as overall. Highly cited papers as well as a special set of papers called Hot Papers are available and can be searched. Another unique feature is the listing of research areas called Research Fronts, algorithmically derived topics reflecting research intensive and breakthrough areas of current science. Tabular data on citations per paper baselines and citation percentiles are presented for each field of science. Brief editorial discussions provide guidance on data analysis and interpretation and enhance the tables, charts, and other data sets presented in the product. An editorial feature called Special Topics gives special attention to selected areas of research. The main methodology page, containing all links, can be found at: http://sciencewatch.com/about/met/
Q: What types of papers are counted?
A: Papers are defined as regular scientific articles, review articles, proceedings papers, and research notes. Letters to the editor, correction notices, and abstracts are not counted. Only Thomson Scientific-indexed journal articles, or papers, are counted.
Q: What are the citation thresholds?
A: The citation thresholds are set to select roughly the same proportion of entities from each field. For scientists the top 1% of names is selected for each of the fields. This percentage of inclusion translates into a specific citation frequency cutoff for each field. For institutions this percentage is also 1%, but for countries and journals 50%. Highly cited papers are selected based on the top 1% by field and by year. Hot papers are in the top 0.1% for each field and bimonthly period. The Citation Thesholds are updated bimonthly and can be found at: http://sciencewatch.com/about/met/thresholds/
Q: What are baselines?
A: Baselines are measures of cumulative citations per paper across large groups of papers that provide expected citation rates for groups of papers in a specific field and year. Since citation frequency is highly skewed, with many infrequently cited papers and relatively few highly cited papers, average citation rates should not be interpreted as representing the central tendency of the distribution, but rather as guidelines or benchmarks. Similarly, percentiles, or other fixed percentage cuts, indicate the citation rates for specific top segments of the citation distribution. Thus baselines provide comparative averages and percentiles provide comparative proportions.
Q: Where can I find definitions for the fields used in ESI?
A: The Field Definitions list can be found at: http://sciencewatch.com/about/met/fielddef/
Q: How can papers be ranked?
A: Papers can be ranked by total citations, journal title, and publication year.
Q: How can scientists, institutions, countries and journals be ranked?
A: Scientists, institutions, countries and journals can be ranked by total citations, total papers, citations per paper, and alphabetic by name.
Q: What criteria are used to determine a highly cited paper?
A: Since citation rates vary by field and older papers are cited more than recent papers, the selection procedure for highly cited papers takes these factors into account. The first step is to count the number of papers cited at different levels of citation and construct distributions for each field and year. These distributions are then used to set selection thresholds by taking the same fraction of papers for each field/year.
Q: What are hot papers?
A: Hot papers are papers that receive citations soon after publication, relative to other papers of the same field and age. Hot papers are selected based on a current two month citation window looking back only two years. A 0.1% threshold is applied to each field and bimonthly period over the two year span.
Q: What criteria are used to determine a hot paper?
A: A paper is selected as a hot paper if it meets a citation frequency threshold determined for its field and bi-monthly group. Citation frequency distributions are compiled for each field and group. Thresholds are set by finding the closest citation count that would select the top fraction of papers in each field and period. The fraction is set to retrieve 0.1% of papers.
Q: What is meant by the term percentile?
A: The term percentile denotes a citation threshold at or above, which a fixed fraction of papers fall when the papers are ranked in descending order by citation count. The term percentile is used to indicate a fixed fraction of top papers ordered by citation count. The levels we have selected for listing by field and year are 0.01%, 0.1%, 1.0%, 10%, 20.00%, and 50.00% (50% corresponds to the median citation value).
Q: What is a research front?
A: A research front is a group of highly cited papers, referred to as core papers, in a specialized topic defined by a cluster analysis. The cluster analysis is based on the number of times the papers are cited together, or co-cited. Research fronts offer an alternative classification scheme for highly cited papers since the assignment of papers to a research front is not based on the journal categories used in Essential Science Indicators or on the words appearing in the papers, but purely on citation patterns.
Q: What journals are included?
A: Counts are based on a journal set categorized into 22 broad fields. Fields are defined by a unique grouping of journals with no journal being assigned to more than one field. The Multidisciplinary field contains journals such as Science and Nature, and individual articles in these journals are assigned to one of the 22 broad fields by a special analysis of their citations and references. The Journal list is updated bimonthly and can be found at: http://sciencewatch.com/about/met/journallist/
Q: What are the broad fields into which journals are classified?
A: The broad fields into which journals are classified are: Agricultural Sciences, Biology & Biochemistry, Chemistry, Clinical Medicine, Computer Science, Economics & Business, Engineering, Environment/Ecology, Geosciences, Immunology, Materials Sciences, Mathematics, Microbiology, Molecular Biology & Genetics, Multidisciplinary, Neuroscience & Behavior, Pharmacology & Toxicology, Physics, Plant & Animal Science, Psychology/Psychiatry, Social Sciences and Space Science. The rules for classification of papers from multidisciplinary journals can be found at: http://sciencewatch.com/about/met/classpapmultijour/
Q: How are institution counts determined?
A: Institution counts are based on the author affiliations given on the published papers. A paper is attributed to an institution if the paper carries at least one author address of that institution. All addresses are considered, not only the first-listed author address. If an institution appears more than one time on a paper, it is considered only once for the determination of paper and citation counts. All unique institutions on a paper are credited equally for the paper, and all citations received by a paper are credited to each of the institutions on the cited paper. No restrictions are made on the citing items in compiling the citation counts, other than that they are recorded from Thomson Scientific-indexed journals only.
Q: What is the time period for counts (cites, papers, cites per paper)?
A: The time period for counts is 10 years, plus partial year counts for the current year (data is updated every two months). This means that any papers in the 10+ year period can be cited by any items in that same period. Database years (the actual years when items are entered into the database, which are slightly different from the publication year) are used to define the time periods. After an 11 year time period is reached, the file reverts to a 10 year plus two month time span for the next bi-monthly update.
Q: How are average citation rates determined?
A: Average citation rates are calculated for each year of the 10 year period based on an accumulation of citations from the year of publication to the current year. The averages are calculated by adding up the citation counts of individual papers and dividing by the number of papers.
Q: What is institution name conflation?
A: Institution name conflation is when institutions having the same name may represent more than one institution. This might be a similarly named institution in some other geographic location. Examining highly cited papers for such an institution reveals whether institutions at different locations are involved.
Q: What counting methods are used for articles and citations for a country/territory?
A: Country counts are based on the institutional affiliations given on published papers. A paper is attributed to a country/territory if the paper carries at least one address from that country/territory. All addresses are considered, not only the address listed first. If a country/territory appears more than once on a paper, then that paper is counted only once for that country/territory. All unique countries/territories on a paper are credited equally for the paper. All citations received by a paper are credited to all the countries/territories on the cited paper. No restrictions are made on the citing items in compiling the citation counts, other than that they are recorded from Thomson Scientific-indexed journals only.
Q: How are country name changes and unifications handled?
A: Country names have been unified to reflect name or country/territory boundaries that have changed. For example, West Germany and East Germany have been unified to Germany for the ten-year period. The United Kingdom has been treated as a single country/territory, rather than having separate entries for England, Scotland, Wales and Northern Ireland.
Q: How are ranking ties handled?
A: Country, institution, author and journal ranking ties are listed alphabetically by entity name.
Q: How can I compute a relative citations per paper value for an author, country, institution or journal?
A: The citations per paper average given in the rankings can be made relative to a world average by dividing it by the "All years" average in the Average citation rate table in the Baselines section. A ratio greater than one indicates that the average is greater than the world average for its respective field.
Q: Why is my paper not in Essential Science Indicators?
A: There may be several reasons why a paper is not in Essential Science Indicators. These are two areas to consider: Papers Rankings and Scientist Rankings.
Papers Rankings:
1. Only articles and reviews are included in Essential Science Indicators. Is your paper a different type?
2. The time period for Essential Science Indicators is based on the database year, that is, the year the paper is entered into the Web of Science. Papers published either very late or very early in one year, may be processed in the Web of Science in a year different than the publication year that appears on the paper. This will affect whether the paper meets the threshold for papers published for that year.
3. What field and year is the paper in question? Go to the InCites website from Web of Knowledge home page. Scroll down in the left hand column to ‘Journal List’ Locate the journal title to determine the field to which your paper has been assigned.
4. What threshold is being used for the top 1% for papers for that field and year? In Essential Science Indicators, go to Citation Analysis – Baselines. Click on the View Percentiles Table and go to the field in question.
Scientists Rankings
Scientist rankings are based on total citations to the scientist’s papers in a specific field. Go to the InCites website from Web of Knowledge home page. Scroll down in the left hand column to ‘Journal List’. Locate the journal title to determine the field to which your paper has been assigned. If they are spread across more than one field, your citations in that field will be less than your overall citations, and therefore you may not appear in the top 1%.
Q: How can I determine whether the number of citations received by a paper is higher than expected for its field and age, or what percentile it falls into?
A: The total citation count for a paper in a specific field and year can be compared with the average citation rate in the Baselines section. If the citation count is greater than the average for the appropriate field and year, then it has exceeded the expected value. The level of citation can also be gauged by finding the closest percentage in the Percentiles table for the appropriate field and year. The available Percentile levels are 0.01%, 0.1%, 1.0%, 10%, 20.00%, and 50.00% (50.00% corresponds to the median citation value). The percentage value indicates the fraction of papers in that field and year having that number of citations or greater.
