The divorce rate in the u. s. rose steadily since the nineteenth century. in his interview with dalton conley, andrew cherlin suggests that one of the reasons for this paradox of the increasing divorce rate at the same time the "love of marriage" persists is due to

The answer is:  

The idea of individualism that has flourished in America since the Colonial period.

Explanation:

Significant changes were brought in the organization of work and family life since the 1970s:  

increasing divorce rates

decreasing marriage and fertility rates

increasing participation of women in the workforce    

American society lacked norms about the way that members of stepfamilies should act toward each other.