This is a topic which has represented a concern for people since the very early stages of science development. The importance of such subject is also underlined by political systems in the past centuries that, in a way or another, encoraged people to get married as early as possible by granting them, for example, a better tax regime or multiple benefits. In my opinion the strongest argument for requiring people to get married is for them to form a family, and give birth to kids, thus increasing the population.