This is an interesting question.
I would say that the most effective type of birth control policy, especially from an economic point of view, is education. The more education people have of the issues, the better people will be. In other words, preventative care is most effective. And when it comes to this topic, education is central. Education will teach people of many things: the dangers of teen pregnancies, diseases, and types of birth control, to name a few things.
Education also plays a dual role. The way people advance in society is usually through education. So, through education, people can become better equipped to face society.