I did this holiday in 2003 and it was fab. You'll have a great time. Group size when I did it was 40.
JY will be able to confirm size number on the trip you're doing.
I've done about 10 JY holidays and all have been great.
Women tend to outnumber men. Age ranges from 20's to late 70's (mainly over 50) but don't let that put you off.
Small group size has been 13 and largest 40.
I'm sure you will have a great time in China.
Anna