The  growth in  one -person  households  in  the United States since the mid  1800s is  one of  the largest  changes in household  composition  during  this time. While  in 18 50, about 2  percent of  all  households  contained one person,  this rose  to 27 percent by  2010  (see Figure 1) .  This  extraordinary growth  likely  reflects  a variety  of  fac tors, including  gains in  life expectancy , improved  health at older ages,  improve d  economic well -being  of the older population,  an increasing age at first marriage in the latter 20 th century, and  shifts  in  the   acceptability of young  women living  alone.