what event caused the population boom (baby boom) in China in the year
1966-1970, 1986-1990, 2016-2020? The graph that I'm looking at is from
http://www.census.gov/cgi-bin/ipc/idbpyrs.pl?cty=CH&out=s&ymax=250

The Chinese like to give birth in an auspicious year
- the Year of the Dragon is supposed to be very popular
- in 1988 a guy I knew remarked how all the women seemed to be pregnant

http://en.wikipedia.org/wiki/Dragon_(zodiac)
<snip>
The Dragon is also the most popular zodiac year. During the Year of
the Dragon, there is a noticeable increase in birthrates in China, as
many parents wish to have a child whose zodiac sign is the Dragon.
</snip>


- can you check that ?

you can see that in 2000 there is no spike in population. So the
zodiac could be one factor. There must be something else too.