Eighty-six per cent of young adults in the US expect their marriages to last a lifetime, even though half of all marriages end in divorce, a new study suggests.

The Clark University Poll of Emerging Adults also found that 57 per cent of Americans aged 18 to 29 feel it is wrong for two people to have sex if they are not emotionally involved with each other. And 73 per cent of the 1,029 respondents from across the US who participated in the study believed that couples should walk down the aisle and exchange wedding vows before having a child.

Jeffrey Jensen Arnett, a psychology professor at Clark University, a small liberal arts college in Worcester, Massachusetts, said the results indicated how optimistic young Americans feel about marriage.

“They grow up knowing that half of marriages end in divorce, yet nearly all of them expect to be in the half that doesn’t,” said Prof. Arnett, who led the study conducted through mobile phone, telephone and internet interviews.

“Of today’s emerging adults, the ones with divorced parents are often the ones who are most determined to avoid divorce, even though they are statistically most likely to get divorced themselves.”

The study revealed, however, that 61 per cent of young American adults expect to give up some of their career goals in order to have the family lifethey want.

“Traditionally, women have been far more likely to sacrifice career goals for family,” said Prof. Arnett, whose study had a margin of error of plus or minus 3.06 per cent.

“These new findings suggest this may change in the new generation of emerging adults to a more equal sharing of family responsibilities.”