Part-time working mother is the norm Ellena Thoma with her 22 month old daughter Georgiana. More Australian women are going back to work after having children, but they prefer to work part-time and the age of their children when they rejoin the workforce is getting younger. A new report - Parents Working Out Work - shows the proportion of mothers in employment has risen from 55 per cent in the 1991 census to 65 per cent in 2011. Half of mothers now return to work by their child's first birthday, compared with 39 per cent of mothers in 1991. Waving goodbye to the baby boom: Prime Minister Julia Gillard and Treasurer Wayne Swan delivered a budget that slashed the baby bonus. Thirty-six per cent of mothers with children under 18 work part-time, up from 28 per cent two decades ago. One quarter of mothers work full time, up from 23 per cent. The Australian Institute of Family Studies research tracked changes in parental employment over the past 20 years. Social researchers attribute the growth to higher educational qualifications, the rising cost of living and changing social attitudes. Researcher at the institute Jennifer Baxter said part-time work meant women didn't have to disengage from work or home life. "It's all about part-time work," she said. These hours enable mothers to retain some time at home caring for their kids, and keep some involvement in paid work. Experts said last week's budget decision to slash the baby bonus marks the end of Peter Costello's baby boom and signals a switch in government focus to boosting economic productivity in tough financial times. The proportion of couple families with a single income earner who works full time - usually the father - has fallen from 32 per cent to 28 per cent in the past 20 years. The baby bonus was a fertility policy, not a workforce policy, University of Sydney Professor of employment relations Marian Baird said. The fertility debate has largely abated; the issues about labour force size and productivity are much more to the fore of government policy thinking, of both Labor and Liberal persuasion. According to the AIFS report, women who work for at least 10 of the 13 months before the birth are more likely to rejoin the workforce sooner after their child is born. Just over three-quarters of the 2600 women surveyed had returned to work by the time their child was 13 months old, and on average returned when their child was 6½ months old. Three-quarters returned to their old job, and of these, 60 per cent went part time. University-educated women in permanent professional occupations are more likely to return to work by the time their child is one. The proportion of couple families where both parents work full time has not changed in 20 years; they still account for one-fifth of families. In contrast, the proportion of couple families with one full-time and one part-time income earner rose from 27 per cent to 34 per cent in 2011. Dr Baird described this as the "one plus" breadwinner model, with mothers usually the "plus." "It has become a social norm," she said. Women expect part-time work, and assume its availability, after childbirth. They ask employers for it. But Dr Baird warned women paid a price for part-time work, experiencing downgraded career options, fewer opportunities and reduced pay. Ms Baxter said there are gendered patterns of employment. Not every job has flexibility Ellena Thoma always knew she wanted to return to work after having a baby. "I enjoy work, I love the company," the 34-year-old from Concord said. Plus I spent that much time and effort completing a university degree and ... building up my career, I felt it would be a shame not to return to work. Ms Thoma said cost-of-living pressures in Sydney influenced her decision. I also think it's good for mothers to spend time interacting with adults rather than children. When Georgiana was born in mid-2011, Ms Thoma took a year's maternity leave from her job as a project manager at FDC Construction. I wanted the first year off, I wanted to enjoy something of her. Her only source of income during that time was the taxpayer-funded parental leave scheme, which pays recipients the minimum wage for 18 weeks. Ms Thoma extended her unpaid leave for another six months and returned to work part time earlier this year. But Ms Thoma said her role requires her to work full time, so her parents look after Georgiana while she works. I would have loved to have been part time ... but it doesn't work in the position I'm working in. You need to spend time on site," she said.