Yahoo! News - Are We Grown Up Yet? U.S. Study Says Not 'Till 26  

The poll found the following ages at which people expect the transitions to grown-up status to be completed: Age 20.9 self-supporting; 21.1 no longer living with parents; 21.2 full-time job; 22.3 education complete; 24.5 being able to support a family financially; 25.7 married; and 26.2 having a child.
'There is a large degree of consensus across social groups on the relative importance of the seven transitions,' said Tom Smith, director of the survey. 'The only notable pattern of differences is on views about supporting a family, having a child and getting married.
'Older adults and the widowed and married rate these as more important than younger adults and the never-married do,' he added. 'This probably reflects in large part a shift in values across generations away from traditional family values.'
The most valued step toward reaching adulthood, the survey found, was completing an education, followed by full-time employment, supporting a family, financial independence, living independently of parents, marriage and parenthood.