Geographic Distribution and Seasonal Variation of Sex Ratio at Birth in India

Abstract

From the data of Indian Vital Statistics in 1962-1964, the geographic distribution of sex ratio at birth and seasonal variation of the ratio in different states of India are studied. In the yearly average of these three years, higher sex ratios at birth distribute in the northwestern inland states than in the southern and eastern coast states. In Rajasthan and Uttar Pradesh the sex ratio is over 120 males to 100 females, which is higher than the highest ever known in Korea. The seasonal variation of sex ratio at birth in the northwestern inland states is more distinct than that in the southern and eastern coast states, as well as the seasonal variation of birth ratio. Both curves of the seasonal variation of sex ratio and of birth ratio have some phase difference, and the sex ratio is rather low in the months of higher birth ratio, and vice versa. Although Indian vital statistics is not yet satisfactorily established, peculiar geographic distribution and seasonal variation of the sex ratio, which seem to be influenced by climate, are perceived. To interprete the phenomena some hypotheses are adapted and discussed.