A An Application of Bradford’s Law for the Covid-19 Research Output Indexed in Web of Science during 2020 – 2025

Abstract

The COVID-19 pandemic triggered an unprecedented surge in scientific publications across diverse disciplines, including medicine, virology, public health, and biomedical sciences. Understanding the distribution of this rapidly expanding body of literature is essential for identifying key sources of scholarly communication. This study applies Bradford’s Law of Journal Scattering to examine the distribution and concentration of COVID-19 research articles indexed in the Web of Science (WoS) database during the period 2020–2025. The primary objective is to identify the core (nucleus) journals contributing to the field and to verify the applicability of Bradford’s Law using established mathematical models. Bibliographic data were retrieved using the keyword “COVID-19,” yielding a total of 21,762 publications distributed across 3,733 journals. The analysis categorizes journals into Bradford zones to determine the concentration of research output and to assess the conformity of the observed distribution with theoretical expectations. The findings of this study provide valuable insights for researchers, librarians, and policymakers in identifying influential journals and understanding publication patterns in pandemic-related research. The collected data were categorized by document type, and only journal articles were selected for analysis, resulting in a dataset of 20,935 articles published across 3,294 journals. This study aims to identify the core journals and assess the applicability of Bradford’s Law using established mathematical and theoretical models.
Bradford’s zoning technique was applied to classify journals into three distinct zones, each contributing approximately one-third of the total number of articles. The distribution was further validated using the Leimkuhler logarithmic model, resulting in the construction of a Bradford–Leimkuhler curve. In addition, Egghe’s theoretical formulation was employed to interpret the characteristics of the three Bradford zones. The study also analyzed key bibliometric indicators of the most productive journals, including impact factor, h-index, publication origin, and the countries of publication.
The results demonstrate a strong conformity of COVID-19 research publications to Bradford’s Law, revealing a highly concentrated core (nucleus) of journals, followed by two successive zones characterized by exponentially increasing numbers of journals with decreasing productivity. Verification through the Leimkuhler model confirmed a logarithmic growth pattern, thereby supporting the applicability of Bradford’s Law. Egghe’s model further elucidated deviations observed in the peripheral zones as a natural outcome of inequalities in journal productivity. Overall, this bibliometric investigation provides valuable insights for researchers, librarians, and policymakers in identifying influential and essential journals within the domain of COVID-19 research.