1 LITIGATING EQUAL PAY FOR EQUAL WORK IN JAPAN, 2012-2020 Charles Weathers a , Shinji Kojima b , Scott North c a Department of Economics, Osaka City University, Osaka, Japan ORCiD: 0000-0002-7490-8842 b (Corresponding author) College of Asia Pacific Studies, Ritsumeikan Asia Pacific University, Oita, Japan Correspondence address: College of Asia Pacific Studies, Ritsumeikan Asia Pacific University, 1-1 Jumonjibaru, Beppu-shi, Oita 874-8577 Japan Email: skojima@apu.ac.jp ORCiD: 0000-0003-0315-8527 c Graduate School of Human Sciences, Osaka University, Osaka, Japan ORCiD: 0000-0002-5576-7837] Abstract: Litigation and courts have been important arbiters of labour policy reforms aimed at redressing Japan's growing social inequality. This article considers seven lawsuits brought by non-regular workers, who sought to use Article 20 of the 2012 Labour Contracts Act to gain equal pay for equal work. All seven cases reached Japan's Supreme Court amid Abe Shinzō’s 2018 labour reforms. The Court’s interpretations reaffirmed employer discretion in categorising employees as a reasonable principle, albeit one which limits the law’s power to redress wage inequality. However, the Court also found the non-provision of various minor benefits to be unreasonable. These outcomes evince a pattern in which litigation marginally transforms reformed labour policy into institutional support for greater equality of compensation and benefits between workers of different statuses. More than advancing equal pay for equal work, the outcomes of these cases support recent government-industry campaigns to boost productivity by encouraging increased use of job-based treatment and diversifying Japan’s employment system. Key words: equal pay for equal work; inequality; Japan; non-regular employment; Work Style Reform Japan has long maintained a two-tier employment system. Seiki (regular) employees, especially in large firms, generally enjoy strong job protection and life security wages and benefits. Hiseiki (non-regular) workers are typically considered expendable, low-wage labour (see Imai and Sato 2011; Gordon 2017). Cost-cutting pressure since the 1980s steadily expanded the use of non-regular workers and stimulated academic debate on whether their increase represents progress or regress in Japanese labour relations (Hanami 1999). Among comparatively low-paid non-regular workers, who may perform similar or equally responsible tasks to those of regular employees, there is a growing feeling of unfairness. While left-wing critics have long criticised unequal treatment as discriminatory, it has only