To emphasize what Nasif and Hans Rosling are saying, I'd suggest playing with Hans's program, gapminder, itself on
http://www.gapminder.org/world.
In particular, check Bangladesh, and try combinations of the following axes:
- Children per woman (fertility rate)
- Contraceptive use amongst adult women, %
- Children per woman (fertility rate)
Try out other measures in the axes too, check other nations to see how we compare wuth them, and see what correlations you can draw.