Check out this page that clumps countries according to the ratio of male:female births.
Japan has a ratio of 1.05, China 1.15, which seems to be the East Asian spread. The Japanese prefer girls and unlike other East Asians seem to have successfully discouraged gender selective abortions.
The South Asian nations have sex ratios of 1.05/1.06, the same as the United States, despite the stereotype that sons are preferred. Why could this be? It might be that sex selective abortion is not accessible to most of the population because of monetary concerns. Additionally, South Asians may be more prone to carry more girls to term compared to East Asians , so sex selective abortions do not skew the ratio as much (I assume Japan at 1.05 is close to the natural rate of many East Asian populations, perhaps even shifted toward girls a bit because of couples that manage to find out gender in a country where 75% perfer girls) .
Finally, take a look at the countries with the most balanced sex ratios. Very interesting, do you see any pattern?
 There are many possibilites, more male fetuses might be spontaneously aborted, or, there might be more genetic males who did not develop the sex characteristics and so are recorded as female. Please note that abortion is illegal in Pakistan and Bangladesh, but legal in India. Nevertheless, the three countries have about the same sex ratio….