Temporal Evolution of Bradford Curves in Specialized Library Contexts

TL;DR

This paper extends Bradford's law formulas to better predict the evolution of Bradford curves over time, accounting for integer constraints and core journal productivity, validated with empirical data.

Contribution

It introduces an extended formula for Bradford curves using the Simon-Yule model, explaining shape deviations and predicting curve evolution in library contexts.

Findings

Extended formulas accurately predict Bradford curve evolution.

Integer constraints cause deviations from the theoretical J-shape.

Empirical validation confirms the model's effectiveness.

Abstract

Bradford's law of bibliographic scattering is a fundamental principle in bibliometrics, offering valuable guidance for academic libraries in literature search and procurement. However, Bradford curves can exhibit various shapes over time, and predicting these shapes remains a challenge due to a lack of causal explanation. This paper attributes the deviations from the theoretical J-shape to integer constraints on the number of journals and articles, extending Leimkuhler and Egghe's formulas to encompass highly productive core journals, where the theoretical journal number falls below one. Using the Simon-Yule model, key parameters of the extended formulas are identified and analyzed. The paper explains the reasons for the Groos Droop and examines the critical points for shape changes. The proposed formulas are validated with empirical data from literature, demonstrating that this method can effectively predict the evolution of Bradford curves, thereby aiding academic libraries in the procurement and utilization of scientific literature.