why the ratio of female birth is more than males?

Answer 1

It is, but not by much.
In reptiles, the warmth of the hatching is what makes the decision on whether the hatchling will be male or female.
That is to say, on warmer occasions, there will be more males than females, but on cooler occasions, there will be more females. (Reptile eggs depend on the weather for successful progeny, since they don't sit on their eggs). Some have speculated that this may have been the reason for the extinction of the dinosaurs. (my own view is more pragmatic. I think dinosaurs are still amoung us, just in different forms).

Also, I've read about a study done on women who have a more acid diet prior to concieving as compared to women who have a alkaline diet. The ones with an acidic environment tend to concieve girls and the ones with an alkaline environment tend to concieve boys, although this has been complicated by when in the woman's cycle all the coital activity takes place. For instance, if coital activity takes place before ovulation, the "X" (female) carrying sperm live longer, and tend to survive to make it to the egg. Whereas a "Y" carrying sperm has more success at the moment of ovulation. (Ovulation is approximately 3 day window of opprotunity)

Another factor to consider is the resilience of the female, which is demonstrated in the ratio of survival in premies. A prematurely born female has nearly double the chance of survival than a male.

Answer 2

In some countries it is due to infanticide of baby girls. It also might be a factor in abortions. What a horrific, godless society!

Also, the technology to sort male sperm from female sperm has been around for three decades. That is useful for dairy cows, but its use by wealthy men is practiced.

Answer 3

Well, X sperm tend to be more robust. Not sure if that would play a part.

Answer 4

Female sperm is stronger than male sperm so male sperm has to fight harder....