How has the use of academic journals changed since the academic library purchase policy changed from selective journals based on core journals to package purchases by big deal? The purpose of this study is to analyze the effect of supply and size of academic journals in university libraries on the use of journals. For this purpose, this study used the actual usage statistics of e-journals of K Academic Libraries during 2013-2015. The analysis shows that there is a so-called long-tail shape in which demand shifts to niche products that are effective in online platforms. Analysis of the use of academic journals by year for three years showed that the use of electronic journals in K Academic Libraries appeared to be a perfect Pareto shape, which is concentrated in the top 20% of journals. In particular, in 2015, the top 5% of journals accounted for nearly 80% of the total usage. Despite the changes in the supply method and size of academic journals, users' use of journals was still concentrated in core journals.