"When studying income differences and income distribution, the self-employed are often excluded from the population studied. There are several good reasons for this, for example that incomes from self-employment are not reported to the same extent as incomes from being an employee. On the other...

"It is well known that children reared in non-intact families on average have less favorable educational outcomes than children reared in two-parent families. Evidence from the United States and Sweden indicates that living in a non-intact family is correlated with lower educational attainment....