a single mother are only 50 percent more likely to engage in criminal activity than children raised with both parents, all else being equal. As shown in table A.2, using this more aggressive approach yields an estimate that family fragmentation is responsible for about $29 billion in costs to the justice system as opposed to the $19.3 billion estimate used to generate the main result of this study.
The $29 billion estimated cost of family fragmentation to the justice system is either too high or too low depending on the true magnitude of any exogenous effects of marriage on criminal activity. The $19.3 billion figure represents about 8.7 percent of all costs to the justice system ($19.3 billion / $222.8 billion = 0.087), while the $29 billion figure represents 13 percent of all costs to the justice system ($29 billion / $222.8 billion = 0.13).
To put these two estimates in context, note that, according to the Bureau of Justice Statistics, in 2002 only 43.6 percent of inmates report that they lived with both par- ents “most of the time” while growing up.54 While the majority of inmates did not live with both parents most of the time while growing up, the figure used to gen- erate the main estimate of this study suggests that only 8.7 percent of the costs of the justice system can be attributed to family fragmentation. As stated previously, Sampson and his colleagues endeavor to control for selection effects and find that former juvenile offenders commit fewer crimes as adults when married. Because our estimates here ignore these potential taxpayer savings from marriage, our method is more likely to underestimate than overestimate the taxpayer costs of fam- ily fragmentation to the justice system.
3. Ignoring any impact of marriage on single fathers understates the taxpayer cost of family fragmentation.
Research suggests that married men become more committed workers at least in part as a result of marriage. Therefore, if single fathers were to marry, it is likely that their labor supply would increase leading to increased tax payments. Further, tables 4–6 show that single-father households have higher take-up rates of antipoverty pro- grams than married households with similar incomes.
Adding a second wage earner would render single-father households less likely to receive government assistance via increased income and economies of scale. Economies of scale via marriage—essentially “savings from size”—imply that by liv- ing together, two adults are better able to share expenses and escape poverty. Ribar provides an example of how marriage leads to economies of scale:
Consider the outcomes for a couple with a 9th–11th grade education and one child in 2001. The median annual income for a woman with this level of edu- cation was $10,330, while the median annual income for a similarly educated man was $19,434. If the mother and child lived apart from the father, their income would have been below the two-person poverty threshold of $12,207; however, if the family lived together, their combined income would have