The most important factor in the decision among couples to have a second child is whether or not the wife has a job, according to analysis by Prof. Jung Mi-ra at Gachon University of Medicine and Science.

Based on a survey between 2008 and 2010 of 177 households who had a second child and 555 households who had only one, the prime determining factor was whether the mother had a job.

Among the couples who had a second child, 73 percent of mothers were full-time housewives and only 27 percent were employed. There were many full-time housewives among couples who decided not to have a second child but a larger number of women with jobs at 38 percent.

The statistics show that working women tend to favor having only one child.

The mother's age is another important factor. Some 62 percent of the housewives who had a second child were under 30 and had been married for a shorter period than those who were over 30.

Of the women who had only one child, only 46 percent were under 30.

The husband's satisfaction with his marriage also plays a role. The survey rated a couple's marriage on five levels and found that the higher the satisfaction, the more likely a couple were to have a second child.

A couple's income is another important factor. Among the couples who had a second child, 51.4 percent were in the low-income bracket and earned less than W3 million (US$1=W1,118) a month.

"The younger the mother and the higher the father's satisfaction with his marriage, the higher the chances that a couple will have a second child," Jung said. "The government needs to make it easier for working women to balance their jobs and families."