 This is however not true for single women, who are usually poorer, for whom social sterility still exists.Due to polyandry and hypergamy, twice as many men in history have been childless than women.From 2007 to 2011, the fertility rate in the U.S. declined 9%, the Pew Research Center reporting in 2010 that the birth rate was the lowest in U.S. history and that childlessness rose across all racial and ethnic groups to about 1 in 5 versus 1 in 10 in the 1970s.