Why do contraceptive practices work for some couples and not for others? How do couples decide the number of children they want? What are the implications of family design in terms of the "population explosion?"Family Design is a thoroughly documented study undertaken by Social Research, Inc., for the Planned Parenthood Federation of America. Based on intensive interviews with 409 husbands and wives, it applies the framework of family sociology to a problem that has previously been studied mainly from the demographic point of view.