Abstract
This paper aims to investigate the editorials of national and local newspapers in Post-War Japan （1970–2019） for ideological bias, source originality, and influential trends. A total of 2,211 editorials from 50 national and local newspapers were collected and analyzed. The selection was limited to editorials published around Constitution Day （May 3）, from 1970 to 2019. I analyzed the text on two bases: （1） the extent to which local newspapers used Kyodo News as source material in their editorials; and （2） ideological tone. I determined that Kyodo News materials were not a major source of editorials, leading us to examine other origins. Once I quantified the liberal or conservative slant in each editorial, I examined the depth of diversity in the left or right tone and the potential factors influencing such leanings.
