Reclassification of Papers in Multidisciplinary Journals for Creation of Thomson Reuters Field Baselines

Each year Thomson Reuters reassigns documents from multidisciplinary journals to their most relevant Web of Science (WoS) subject area. While multidisciplinary journals publish articles on a wide array of topics, individual articles in those journals focus on one area of research. The reclassification process allows these specialized articles to be appropriately compared with articles of similar citation characteristics and topic focus. The rate of reclassification varies widely with journal. For example, for Science, Nature, and PNAS, the average rate of reassignment is much higher--about 95 percent. The benefit of reclassification is that statistics for fields, including author, institution, country, journal and paper analysis, more accurately reflect all papers in these fields, including those found in multidisciplinary journals, some of which publish influential, highly cited research reports.

Prior to 2012, reclassification had been limited to a specific list of journals. In 2012, the methodology for reclassification has been updated in the following ways:

  • Reclassification prior to 2012 had affected a specific list of journals but now extends to all publications in the WoS subject areas MULTIDISCIPLINARY SCIENCES and MEDICINE, GENERAL AND INTERNAL.
  • Reclassification had previously considered both citing and cited papers, which meant that as citations accrued, a paper from Science could have been reclassified in one subject area in 2009 and a different subject area in 2010. Reclassification now considers only cited papers, so there will be less volatility in reclassification from year-to-year.
  • Reclassification efforts had previously been bound to specific years, with more frequent years (>2005) undergoing annual updates. Now all documents from all years in these categories have been reclassified and, going forward, will only be reclassified if a correction is made to its cited references.
  • A document that was eligible for reclassification would have ultimately been assigned to one WoS subject area only, that is, the category assigned to it as a result of the reclassification process. But in WoS, journals can belong to MULTIDISCIPLINARY SCIENCES or MEDICINE, GENERAL AND INTERNAL and another WoS category; the updated reclassification process now considers this, which means a given set of documents classified MULTIDISCIPLINARY SCIENCES is not necessarily mutually exclusive with other WoS subject area(s).
  • Reclassification is applied recursively. Reclassification is not resolved for a given document until all eligible cited references for that document – and for its cited references cited references and so on -- have first been reclassified; a MULTIDISCIPLINARY SCIENCES or MEDICINE, GENERAL AND INTERNAL document that cites a MULTIDISCIPLINARY SCIENCES or MEDICINE, GENERAL AND INTERNAL document, would be reclassified on the basis of the reclassified category of the cited document.

The reclassification process

For each paper, we obtain all the cited references, along with the respective WoS subject areas assigned to the journals in which the cited references occur. We then determine which WoS subject area most frequently occurs; the paper is then reclassified to the most frequently occurring category from this distribution.

For example, if the majority of the cited references of a paper published in MULTIDISCIPLINARY SCIENCES are to documents published in NEUROSCIENCE journals, the paper will be assigned to NEUROSCIENCE. Documents will retain the previously assigned categorization under the following circumstances:

  • There are no subject areas to rank.
  • The most frequently occurring category is the original subject area.
  • There is a tie between the top two subject areas.

Reclassification prior to 2012 had affected a specific list of journals but now extends to all publications in the Web of Science subject areas MULTIDISCIPLINARY SCIENCES (link to http://science.thomsonreuters.com/cgi-bin/jrnlst/jlresults.cgi?PC=D&SC=RO)  and MEDICINE, GENERAL AND INTERNAL  http://science.thomsonreuters.com/cgi-bin/jrnlst/jlresults.cgi?PC=D&SC=PY .