Temporal Evolution of Bradford Curves in Specialized Library Contexts

摘要: The Bradford’s law of bibliographic scattering is a fundamental law in bibliometrics and can provide valuable guidance to academic libraries in literature search and procurement. However, the Bradford’s curves can take various shapes at different time points and there is still a lack of causal explanation for it, so the prediction of its shape is still an open question. This paper attributes the deviation of Bradford curve from the theoretical J-shape to the integer constraints of the journal number and article number, and extends the Leimkuhler and Egghe’s formula to cover the core region of very productive journals, where the theoretical journal number of which fall below one, . The key parameters of the extended formula are identified and studied by using the Simon-Yule model. The reasons for the Groos Droop are explained and the critical point for the shape change are studied. Finally, the proposed formulae are validated with the empirical data found in the literature. It is found that the proposed method can be used to predict the evolution of Bradford’s curves and thus guide the academic library for scientific literature procurement and utilization.