Women tend to outlive men: It has been found that women tend to have higher life expectancy compared to men, which is a biological factor.
Girl babies are resistant to boy babies: Studies have indicated that girl babies have a lower mortality rate as they are more resistant to infections and diseases during infancy, which contributes to a slightly higher overall female population.
Preference for Sons: Gender based families prefer to have sons and often use technologies to ensure birth of more boys which results in an imbalance in sex ratio. Therefore, this is not a factor contributing to a greater female population.
Gender-neutral behaviour: Gender neutral behavior, if present, would not result in such a condition. Also, gender-neutral behavior is largely absent in the world, thus it is not a valid reason for having more females.