The Evolving Marriage Gap in Children's Outcomes: Family Structure and Young Adult Outcomes Revisited

 

• Core Premise: Revisiting Kearney & Levine's (2017) heterogeneous "marriage premium" framework using recent Panel Study of Income Dynamics (PSID) data up to 2023.

• Key Findings:

  1. Childhood Living Arrangements & Trends: Family structure at birth shows stickiness (most children born married stay married; cohabiting unions are much less stable). Births to cohabiting parents have risen (15% in 2000-2009), but cohabiting parents are classified with unmarried mothers because of high instability.

  2. Resources & Gaps at Birth: Real household income for single/unmarried mothers has risen over time (thanks to welfare/tax reforms like EITC), but the income gap between married and unmarried households has widened. However, poverty rates among children born to unmarried mothers have fallen (improving material circumstances).

  3. Early Adult Outcomes (Poverty Avoidance): The marriage premium for avoiding poverty at age 25 has narrowed significantly for children born in the 1990s compared to the 1970s/1980s. Unmarried mothers' children are doing better at avoiding poverty.

  4. College Completion Gaps: In sharp contrast, the marriage premium for earning a 4-year college degree by age 25 persists and remains very wide (roughly 17-19 percentage points). It is concentrated among higher-resourced/college-educated mothers because a college degree requires substantial parental investment and resources, compounded by assortative mating.

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Let's write out the blog post.# The Evolving Marriage Gap in Children’s Outcomes: What Has Changed Over the Last Decade?

For decades, economic research has documented a stark divide between children raised in married-parent households versus those raised by single parents. On average, children of married parents experience better educational attainment, higher earnings, and lower poverty rates in adulthood.

However, looking only at "average" effects masks a more nuanced reality. Back in 2017, economists Melissa Schettini Kearney and Phillip B. Levine proposed a heterogeneous framework arguing that the "marriage premium"—the benefit a child derives from parental marriage—depends heavily on a mother's own resources, the economic contribution of a potential partner, and the specific outcome in question.

In a newly released National Bureau of Economic Research (NBER) working paper, "The Evolving Marriage Gap in Children’s Outcomes: Family Structure and Young Adult Outcomes Revisited" (NBER WP 35765), Kearney, Levine, and co-author Alden Q. Barson revisit this framework using the latest data from the Panel Study of Income Dynamics (PSID) through 2023. Their findings reveal a fascinating divergence: while the gap in young adult poverty has significantly narrowed, the college completion gap remains stubbornly wide.

1. The Shifting Landscape of Family Structure and Childhood Resources

Before examining adult outcomes, the researchers tracked how family structures and household resources have evolved across birth cohorts.

• The Rise of Cohabitation: While the share of children born to married parents has drifted downward (from 75% in the 1970s to 66% in the 2000s), births to unmarried, cohabiting biological parents have surged—rising from 2% in the 1970s to 15% in the 2000–2009 cohort.

• Instability of Cohabiting Unions: Cohabiting relationships prove far less stable than legal marriages. Among children born to cohabiting parents in the 2000s, only 32% are living with married biological parents by age 14, and nearly half (54%) end up living with just one biological parent. Because of this instability, the authors group cohabiting parents with unmarried mothers in their outcome analyses.

• Economic Gains for Unmarried Mothers: Driven by policy shifts (such as welfare reforms and expansions of the Earned Income Tax Credit) and changing labor market participation, the absolute economic well-being of unmarried mothers has improved. The share of children born to unmarried mothers who avoided poverty grew from 55% to 66%. However, because married households also saw income growth, the absolute gap in household income between married and unmarried households actually widened.

2. Poverty Avoidance: A Narrowing Gap

When tracking young adults at age 25, the researchers examined how the "marriage premium" for avoiding poverty has shifted between children born in the 1970s/1980s versus those born in the 1990s.

• The Convergence: For poverty status at age 25, the marriage gap has noticeably narrowed over time.

• Driving Force: This convergence is primarily driven by improvements among children born to unmarried mothers, who are now much more successful at avoiding poverty in early adulthood than previous generations. Meanwhile, poverty rates among children born to married parents have remained consistently low.

• Regression-Adjusted Realities: When controlling for maternal education and background characteristics, the marriage premium for avoiding poverty in the 1970–1989 cohort was positive (roughly 7–12 percentage points for mothers with 10–13 years of schooling). However, for the 1990–1999 birth cohort, that estimated marriage premium is no longer statistically significant across the maternal education distribution.

3. College Completion: The Persisting Divide

While basic economic survival (poverty avoidance) has seen convergence, higher-order educational attainment tells a starkly different story.

• A Stubborn Gap: The marriage premium for earning a four-year college degree by age 25 remains wide, persistent, and substantial across birth cohorts.

• The Divergence: While children born to unmarried mothers experienced modest gains in college completion over time (a 4 to 13 percentage point increase depending on maternal education), their rate of growth has failed to keep pace with children born to married parents.

• The Current Premium: For the most recent cohort, the marriage premium for college completion stands at 19 percentage points for mothers without a college degree and 17 percentage points for mothers with a college degree. Across nearly all resource levels, the college completion premium remains significant at roughly 5 to 20 percentage points over maternal education.

Why Does This Divergence Exist?

The paper's theoretical framework helps explain why poverty gaps and college completion gaps are moving in opposite directions:

1. Thresholds of Investment: Avoiding poverty is a primary outcome that can be achieved once a household crosses a certain basic resource threshold. Because safety net policies and single-mother earnings have improved over recent decades, more families have crossed that baseline threshold.

2. The High Cost of Higher Education: Earning a four-year college degree represents an intensive, multi-year investment of financial and non-financial parental resources.

3. Assortative Mating: Because high-resourced individuals tend to partner with other high-resourced individuals (assortative mating), legal marriage actively compounds household resources. Two highly resourced parents in a stable home are uniquely positioned to provide the financial backing, stability, and cultural capital necessary to propel a young adult through a university degree.

Final Takeaways

The findings of Kearney, Levine, and Barson offer a vital, nuanced update to our understanding of family structure in America.

• The Good News: Economic improvements and targeted social policies over the last few decades have successfully helped single-mother households lift their children out of early-adult poverty, largely closing the poverty marriage gap.

• The Persistent Challenge: When it comes to advanced educational milestones like earning a bachelor's degree, the family structure gap is as wide as ever.

Ultimately, while material living standards for single-parent families have risen, disparities in household resources and higher-order educational outcomes tied to family structure remain a central challenge for social mobility.