If you haven't visited Gapminder -and toyed around with the data, your missing a big part of understanding the world we live in. (Find out more about it through Dr. Hans Rosling's lecture at TED Talks.)
It is an unbelievably great resource and a great way to understand the dynamics of the world. The two charts above for instance show the relationship between fertility (number of children per woman) and level of urbanization (percent of the population that lives in urban areas) vs. the former against the use of contraceptives.
It shows there is a stronger relationship between increasing urbanization and lower fertility rates -even more so than fertility vs. the use of contraceptives. (Although it is clear that urbanization also increases the use of contraceptives among women.)