Evidence of a Growing Inequality in Work Timing Using a Japanese Time-Use Survey

Using data from a Japanese time use survey, we show a noteworthy increase in the share of employees working unusual hours (late night and early morning) over a period of a decade since the mid 1990s. When controlling for changes in hours worked, however, we find that the notable increase in the fraction of people working unusual hours was for low-income nonregular employees (part time, temporary and contract workers), while relatively higher-income regular employees' work timing remains stable. These observations imply that there is a trend of diversification of work timing in Japan between regular and nonregular employees. A possible explanation is that the increase in the average hours worked per weekday by regular employees, possibly because of the spread of the five-day workweek since the 1990s, increased the demand for services and goods during unusual hours, as they returned home. An Oaxaca-Blinder type decomposition suggests that such an increase in the average hours worked by regular employees explains partially the rise in the employment rate of nonregular employees at unusual times. We also suggest that the negative income effect induced low-wage nonregular employees to take jobs at night to earn a wage premium.