This year, for the first time, Highly Cited Researchers from Clarivate Analytics – a list of elite scientists and social scientists identified through analysis of highly cited papers (those ranking in the top 1% by citations for field and year) – will introduce a new Cross-Field category to identify researchers with substantial influence across several fields during the last decade. Some 2,000 with cross-field impact now join approximately 4,000 who have been selected in one or more of 21 broad fields, such as biochemistry, engineering, physics, etc.
An increase of 50% is substantial, but 6,000 researchers still represents a very small fraction of all scientists and social scientists actively publishing today.
Since introducing Highly Cited Researchers in 2014, Clarivate Analytics has received the suggestion from many that limiting the methodology for selection to only those with a required number of highly cited papers in a single field, as defined in Essential Science Indicators (ESI), discriminates against researchers who publish highly cited papers in several fields but not enough in any one field to be chosen.
We responded to this concern. In line with recommendations on best practice, we always want to ensure that any metrics or analysis that we produce is structured and presented in a responsible manner, and extending the identification of Highly Cited Researchers to cross-disciplinary work fulfills that goal.
The challenge for us was finding a method that took account of the different threshold number of highly cited papers in each field so that those contributing papers in several fields could be compared in an equal manner with those selected in one or more ESI fields. The solution chosen was to fractionate the credit for each highly cited paper such that a paper in a field with a high threshold number of papers was weighted less than a paper in a field with a lower threshold number of papers.
An example illustrates the method:
|ESI Field||First Name||Last Name||Number of HCPs||Citation to HCPs||Field Citation Threshold||Field Paper Threshold||Field Paper Score||Field Citation Score|
The fictional researcher Joseph Savant published 15 highly cited papers in the period 2006-2016 in four ESI fields. Seven papers in Field 6, with a threshold number of eight for selection, earned Savant a credit of .875 (or 7/8ths). Three papers in Field 14, with a threshold number of six for selection, were worth .5. The sum of the fractional paper counts in each field yielded a total Cross-Field paper score of 1.67. A score of 1 or more indicates that the individual achieved equivalent impact to a researcher chosen in a specific ESI field.
The second criterion for selection as a Highly Cited Researcher is enough citations to rank in the top 1% by citations for a field. Again, citations in different fields were fractionated in a similar manner to the treatment of papers. In the example above, Professor Savant earned more than five times the number of citations needed for selection as an influential cross-field researcher. Both criteria had to be met for selection as a cross-field Highly Cited Researcher, just as required for selection in one or more ESI fields.
Traditional field definitions are useful in some contexts but less so in others. Today, an immunologist may identify herself as a biochemist and a molecular biologist. Another researcher may be hard pressed to say whether he is a chemist, materials scientist, or engineer. Breaking through the artificial walls of conventional disciplinary categories will help keep our Highly Cited Researcher list contemporary and relevant.
Moreover, as frontier areas of research are frequently interdisciplinary, it is even more important to identify scientists and social scientists working and contributing substantially at the cross-field leading edge.