There are several, often contradictory, approaches to determining how many children are ideal for a single family: from the perspectives of parents, children, and society. These numerous areas of research need a tour of what is and isn't known about how the size of a family influences the lives of its members. The number one concern of any parent is providing their child with a happy and healthy life. They want to give their offspring the best chance possible at achieving success in school and in life. Helping them to avoid illness and giving them the opportunity to reach their full potential are other important factors in deciding the right number of children for a family to have. Also considering the impact that having too many or too few children has on a family's ability to have more children later in life is important. Having more children if you can afford it means that your family will be larger then if you didn't have any more children than necessary. If you can't afford any more children then your family will be smaller then if you did have more children. In both cases, having more or fewer children than what would be considered "optimal" affects the entire family. Finally, we must consider how many children are ideal for the environment to support. Since space is limited, we need to make sure that every member of the family gets their fair share.