Male Female Ratio...

While browsing the internet on male-female ratios across the world, I came across this website where they have listed male-female ratios among people of various racial origins in USA.

None of the ratio's have more than 10% difference. In fact many of them have less than 5% difference in ratio. I am positive that the ratio will be similar across the world. In fact, I am equally positive that it will be a less than 10% difference for all such species in the world. (Is there any species where the ratio is skewed?)

Is the only scientific explanation for this, probability?