Family size effects: a review.

Larger families are more frequent with early marriage and rapid birth of the first child. In larger families, child rearing becomes more rule ridden, less individualized, with corporal punishment and less investment of resources. Smaller families tend to result in higher IQ, academic achievement, and occupational performance. Large families produce more delinquents and alcoholics. Perinatal morbidity and mortality rates are higher in large families as birth weights decrease. Mothers of large families are at higher risk of several physical diseases. Common methodological errors are indicated and exemplary studies are described.