The birthrate dropped dramatically during the Great Depression - 1930's.
And that was before the pill (1960's) and other technological advances to curb births.
I happen to believe a child is a great blessing in a family. Unfortunately the expectations of what a child needs in today's world leads many to believe they cannot afford a child. It is undeniable that there are many expenses connected with bearing and raising a family, but there are also many perceived, material needs that are not really necessary for children- clothes, toys, etc. Children do not really need their own bedroom and bath - sharing with a sibling is fine until well into the teen years, when they are near ready to leave home.
As long as children have loving parents and family, they are content.