The transition to adulthood is being stretched from both ends In the 1890s, the average interval between a woman’s first menstrual period and marriage, which typically marked a transition to adulthood, was about 7 years; a century later in industrialized countries it was about 14 years (Finer & Philbin, 2014; Guttmacher, 1994). Although many adults are unmarried, later marriage combines with prolonged education and earlier menarche to help stretch out the transition to adulthood.