For Chinese people years repeat themselves every 12 years, based on the 12 Chinese zodiac signs. Chinese people believe that history repeats itself based on several cycles.
Bad and good birth years
Among these 12 zodiac signs none is bad.
But truth is that some signs are perceived as good while others are perceived as bad. Chinese people believe in this. And they all want their child to be born a good year: such as pig year, monkey year, horse year.
They will carefuly avoid the goat year for instance. In fact the general hold responsible for the down fall of the last Chinese dynastie Qing dynastie were all goats. A chinese saying tell us that among 10 goats, 9 are bad. We note that there is still one good goat. Nothing is fully white or black in China.
What is "bad" years were in fact "good"!As you understand Chinese people don't want to give birth a goat year or any "bad" year.
Therefore there is a real birth difference between good and bad years! sometimes as much as 1 million!
When you think about this, it means more competition for instance to get a place in primary school, to get accepted by the top universities...
Therefore it would be some kind of advantage to be born a "bad year"!