 Each paper in the data is assigned to one or more of 21 categories, based on the ISI classification of the journal in which the article was published.The Highly Cited Researchers list is compiled by selecting, in every field, those researchers with the highest number of highly cited papers in a 10-year, rolling time period.The number of highly cited researchers varies from field to field and is determined accordingly to the total number of researchers contributing to the single field.