Employed Japanese women could surpass 30 million as early as this year, though a shortage of slots at day care centers poses a barrier to taking jobs for 30-somethings raising children.

About 29.91 million women were employed in October, up 110,000 from September to mark a fourth straight month of increases, show survey results out Friday from the Ministry of Internal Affairs and Communications.

The female working-age population has plateaued. But the recent growth in female workers is driven by the middle-age demographic. Women aged 45 to 54 with jobs rose 90,000 on the month, while those 65 and older logged a 30,000 increase. Many mothers are apparently getting part-time jobs when their kids are older.

The tight employment market is also a boon for these women. October saw 1.62 employment openings per job seeker, according to data from the Ministry of Health, Labor and Welfare. Suffering from a serious labor shortage, businesses are offering better pay and conditions, with the average hourly wage for part-timers reaching a record 1,141 yen ($10.05) in September.

But employed women aged 25 to 34 decreased by 20,000, while the 35 to 44 group recorded a drop of 50,000. Many women in these age groups leave their full-time jobs to start families or care for young children. The problem is that mothers, particularly in urban areas, find it difficult to return to work when they would like because day care centers have long waiting lists.

The overall unemployment rate came to 2.4%, with the female rate even lower at 2.2%. Both came in well under the 3% threshold for what Japan considers full employment -- when everyone who wants to work is said to have a job.

That said, addressing the day care shortage remains an urgent challenge in a rapidly aging country that needs all the labor it can get.