Numbers of articles in the three Japanese national newspapers, 1872-2021

Newspapers have been analyzed in many disciplines, including the humanities, social sciences, and natural sciences. However, previous research using Japanese newspapers investigated the absolute frequency (number) of articles of interest and did not examine the relative frequency (rate) of articles, restricting a deeper understanding of humans, society, and nature. The absolute frequency and the relative frequency of articles can show different patterns of results, which leads to different conclusions. Thus, investigating only the absolute frequency of articles is insufficient, or sometimes misleading. Therefore, it is necessary to examine not only the absolute frequency of articles but also their relative frequency. For this purpose, I conducted a series of systematic searches and provided the yearly numbers of articles in the three databases of Japanese national newspapers over the 150 years between 1872 and 2021. This paper enables researchers to calculate the relative frequency of articles, contributing to research in many disciplines.