Maybe they're sterile.

I am of course joshing!!

You may know that in China there is enormous pressure on young people, especially girls, to get married before a certain age. This differs from countryside to city, but generally & traditionally a Chinese girl over the age of 25 is considered already quite old. In Japan they call those girls 'stale christmas cake', it's a lovely phrase. In China they say 老姑娘 (lao gu niang) which has quite negative connotations, like spinster.

So Chinese women who are 33 years old have probably stopped focusing on finding love and instead concerted their efforts on their careers, because they have accepted they will have to look after and be financially responsible for themselves.

Mind you, from a Western perspective 33 is not too old at all! My wife was 42 when I married her! Then again, I was 55.

Is this a fantasy or are there really a billion Chinese women with small butts over 30 that no one wants?
Can I have mulitple wives in China? hmm if I feed dog chow and buy alot of bunk beds, I can afford maybe 20. Naa too much PMSing, maybe 10, still too many,,, 5?
In North America I believe that after 40, a womans chances of getting married drop like a stone. Very few have small butts tho.