It would be like the case of teaching married women about birth control only to discover it was unwed mothers having all the babies!
多年前未婚媽媽的例子，許多人可能還記憶猶新。當家計人員挨家挨戶為已婚婦女解釋節育觀念、避孕方法的同時，嬰兒潮卻來自不在估計之內的「非危險群」﹘﹘未婚媽媽。