a result, in India there are more missing women in developed urban areas, than in rural regions. On the other hand, in Mainland China, rural areas have a larger missing women problem than urban areas. Mainland China's regional differences lead to different attitudes towards the one-child policy. Urban areas have been found to be easier to enforce the policy, due to the danwei system, a generally more educated urban population – understanding that one child is easier to care for and keep healthy than two. In more rural areas where farming is labor-intensive and couples depend on male offspring to take care of them in old age, males children are preferred to females. Even developed countries face problems with missing women. The bias against girls is very evident among the relatively highly developed, middle-class dominated nations (Taiwan, South Korea, Singapore, Armenia, Azerbaijan, Georgia) and the immigrant Asian communities in the United States and Britain. Only recently and in some countries (particularly South Korea) have the development and educational campaigns begun to turn the tide, resulting in more normal gender ratios. Under-reporting Some evidence suggests that in Asia, especially in Mainland China with its one-child policy, additional fertility behavior, infant deaths, and female birth information may be hidden or not reported. Instead of policy expanding women's opportunities for gainful employment policy, from 1979 onward the one-child policy has added upon the son preference causing the largest number of missing women in any country. As parents are eager to have sons and are allowed only one child, some first born females are not reported with the hope that their next child will be a son. The numbers cited for the sex disparity in Mainland China is likely very exaggerated, as birth statistics is skewed by late registrations and unreported births of females: for instance, researchers found that census statistics of women in later stages of their life do not match with the birth statistics, possibly accounting for 25 million of the 30 million missing women commonly cited. In the other direction, migration, especially to GCC countries, has become a larger issue for sex ratio estimates. Because many male migrants move across borders without their families, there is a large influx in the number of males, which would bias the sex ratios towards more missing women, even when there are not. Causes Sen's original argument Sen argued that the disparity in sex ratio