Wages for part-time workers in Japan have been rising as a result of labor shortages in a range of positions in offices, restaurants, and factories—a bright spot in an economy that needs price gains.

Average hourly wages offered to part-time job applicants in Japan’s three major metropolitan areas increased 1.8 percent in March from a year earlier, for the 33rd consecutive monthly gain, according to Recruit Jobs, a Tokyo company that handles job-placement information. Wages in six job categories—including clerical jobs in offices, call-center operations, and data-entry work—were higher.

The gains for part timers—which were even stronger at a record 2.2 percent in February—are outpacing those for full-time workers because employers are turning to them to fill gaps as the shrinking and aging population reduces their workforce.

“It has completely become a workers’ market because of the severe shortage of part-time workers,” said Kuniko Usagawa, senior manager, Jobs Research Center at Recruit Jobs. “It’s getting more difficult to hire people unless companies raise their wages, even if working hours are short.”

Part-time employees composed a record 30 percent of Japan’s labor force in 2015, rising from 13 percent in 1990, according to the labor ministry.

Pay for part-time workers nationwide rose 0.5 percent in 2015, compared with a 0.4 percent increase for Japan’s full-time employees, according to the labor ministry data. The wage increase nationwide is smaller than the gains in the metropolitan areas, because the economic weakness in some smaller cities and rural areas means fewer job openings.

There are limits to the economic benefits that come from wage gains in the part-time category. In Japan’s two-tier employment system, regular full-time workers are typically paid more per hour and have benefits and job security that allow them to spend more. Part-timers with less security and lower overall income are less likely to make a big impact on consumption.