> There are a number of arguments you could make as to why (for example: married people tend older and so are farther in their careers), but it's not just "marr

> There are a number of arguments you could make as to why (for example: married people tend older and so are farther in their careers), but it's not just "married households have two incomes and single households have one". Sure I didn't say it was the only explanation. But it is a sufficient one to prove the relationship is causal.