According to Cohen $(2014),$ the proportion of married$-$couple households had dropped to less than half $(45$ percent$)$ of the total of households by $2010.$ The proportion of individuals living alone rose from $13$ to $27$ percent between $1960$ and $2010,$ and single$-$parent households rose from $6$ to $12$ percent. The dominant married$-$couple household of the first half of the twentieth century was replaced not by a new standard, but rather by a general increase in family diversity. What is NOT the primary reason for these changes?

Gender equality

Market forces

Family rearrangements

Social welfare reform