Ren Lanping could have had a second child without breaking the law, but decided it would cost too much to bring up another.

Ren is a resident of Yicheng county, one of the fourteen regions that the central government chose in the 1980s to test a policy allowing rural families to have two children.

Ethnic groups and families living in remote areas in China also enjoy the exemption to the one-child policy.

Ren in her 40s, is caring for her 18-year-old son while her husband works in the southern city of Guangzhou. Burdened with her son's medical bills and other costs, Ren believes she can't afford another child.

"Raising our child, sending him to school and helping him build house...a child is expensive," Ren said.

Unwarranted concern

The policy was a trial to see whether the relaxed policy would lead to a jump in the county's population.

In 1980s when most rural families were only allowed to have one child, especially in urban areas, Liang Zhongtong, as a Party school teacher in Yicheng, knew the county's farmers were unhappy with the one-child policy.

And it was foreseeable that restricting Chinese to having one child could lead to an aging population and other demographic problems, according to Liang.

He made a suggestion to the central government to allow Yicheng villagers to have two children.

In Yicheng women are only allowed to have a child after they turn 24, and must have a second before they turn 30 under the premise they get married after 23, and men after 25.

The county's policy is different from that of the rest of China. Under China's marriage law, women can get married after they turn 20, while men have to wait till they are 22.

"By delaying the childbearing age (in Yicheng) four years, there will be only four generations," explained An Dousheng, director of Yicheng county family planning bureau.

Before 1985, when large banners displayed "one child is better" were seen everywhere, local enforcers struggled as public opinion stood firmly against the one-child policy.

Che Yuelian, now 66, was then a local enforcer in the county's Xiheshui village. The job was the most difficult one on earth as "villagers cursed and even beat enforcers, which made persuading them extremely difficult," Che said.

But the relaxed policy, allowing farmers to have second child, has dramatically improved relations between the enforcers and villagers.

Like other local cadre, An worried that villagers would want a third child, or even a fourth.

But Yicheng didn't suddenly witness a jump in child births as a result of the trial.

Indeed, two decades on, Yicheng's population growth is much slower than other parts of Shanxi province.

And the male-female ratio in Yicheng is more balanced than the national average. Statistics from the county's bureau show that there are 104 boys to every 100 girls in Yicheng. The national average is about 118 boys to 100 girls, according to the 2010 census.

Dwindling desire

Fertility in the special zones has decreased as economic development and urbanization have increased. The national average TFR (total fertility rate) is less than 1.5 children over a woman's lifetime, which is well below the replacement level of 2.1. In Yicheng, the rate stands at 2.0 children.

The motive for bearing children is changing due to economic development, Liang says.

Ren and her husband are among the 8,430 married couples (about 12.5 percent of those eligible) in Yicheng who have decided not to have a second child.

"People's desire for reproduction has kept weakening and some places in our province have seen negative population growth for several years," Liang said.

China has been fine tuning it one-child policy for years. Shanghai pioneered a policy allowing urban couples who are only children to have a second child. And some rural areas have allowed parents whose firstborn is a girl, to have another child.