According to my guide at the Cu Chi (sp?) tunnels, here are some interesting facts about Vietnam:

75% of the population was born after 1975
80% are under the age of 35
Vietnam is the #1 exporter of rubber, #2 of rice (after Thailand), #3 of coffee (which surprised me) and #5 in seafood.

This guide as well as one other mentioned the family planning program in Vietnam. They are encouraged to have only 2 children and if you work for the government, you can lose your job if you have more. The gov't broadcasts public service announcements (among other things I'm sure) over a loud speaker in the mornings. They also distribute free condoms.