When Women Have More Men to Choose From, Mothers and Babies Fare Better, Study Finds
A growing body of economic and public health research suggests that the balance of men and women in local dating markets can subtly but measurably influence pregnancy outcomes and infant health. A new study in Journal of Public Economics argues that where women have more potential male partners, both mothers and newborns tend to fare better.
The paper, titled The Effect of Dating Markets on Maternal and Neonatal Health, contributes to a growing interdisciplinary conversation about how economic forces and demographic realities intersect with reproductive health and racial disparities in the United States.
The study, led by Krzysztof Zaremba of ITAM Business School in Mexico City, treats romantic partnerships as a market shaped by supply and demand. Zaremba examined whether the availability of male partners affects women’s relationship stability, sexual health and the health of their babies at birth.
Sex ratios and relationship leverage
Economic theory suggests that when men are scarce, women have less bargaining power in relationships, potentially affecting whether and when they marry, how resources are shared and how pregnancies are planned. In the United States, these imbalances are especially pronounced in Black communities, where incarceration and higher mortality among young men reduce the pool of potential partners.
National data show that for every 100 Black women of childbearing age, there are about 89 Black men, compared with roughly 102 men for every 100 White women. Zaremba investigated whether this demographic gap could help explain long-standing differences in maternal and infant health between Black and White Americans.
A central challenge is that adult sex ratios often reflect deeper social and economic conditions. Communities with high crime or low employment may both send more men to prison and experience worse health outcomes overall, making it difficult to determine whether partner availability itself is responsible for observed health patterns.
Using birth records as a natural experiment
To address this problem, the study uses the relative randomness of a baby’s sex at birth. Because the probability of having a boy is around 51%, small communities experience accidental fluctuations in the numbers of boys and girls born in a particular year that are unrelated to local policies or economic conditions.
Zaremba notes that Americans are less mobile than often assumed, meaning the mix of boys and girls born in a county can influence its dating market decades later. He finds that sex ratios at birth remain a significant predictor of adult sex ratios up to 35 years later, particularly in small and mid-sized counties.
Using U.S. birth records from 2011 to 2019, the study analyzes approximately 7 million births. It defines local dating markets according to county, race and five-year age group, then connects historical sex ratios within those birth cohorts with later health and relationship outcomes when the cohorts reach childbearing age.
The analysis concentrates on communities where each birth cohort contains between 200 and 5,000 people. This range allows random variation in sex ratios to emerge without being completely smoothed out in larger populations while retaining enough observations for statistical reliability.
More men, more marriages and fewer risks
The findings suggest that a modest increase in the proportion of men does not change the overall number of children born but does alter the circumstances in which births occur. When dating markets are more favorable to women, births are more likely to occur within marriage and less likely to occur outside it.
The study estimates that a relatively small increase in the local proportion of men raises the rate of marital births by 9.7% from a baseline of 47 marital births per 1,000 women. Over the same shift, non-marital birth rates decline by 11.2% from a baseline of 34.4 births per 1,000 women.
At the individual level, women are nearly 3 percentage points more likely to be married when they give birth if their local dating market contains more men. The proportion of births in which the father is not identified on official records also falls by approximately 1.5 percentage points.
These relationship changes coincide with improvements in several indicators of maternal health. In counties and cohorts with more available male partners, women are less likely to be diagnosed with certain sexually transmitted infections and less likely to experience some pregnancy-related complications.
Health gains for mothers and newborns
Rates of chlamydia diagnosed during pregnancy decline by about 13% compared with an average prevalence of 1.9%. Maternal hypertension, an important risk factor for complications including preeclampsia and preterm birth, falls by roughly 17% from a baseline rate of 2.2%.
Other conditions, including gestational diabetes and syphilis, move in a similar direction in the data, although these estimates are not statistically precise enough to support firm conclusions. Nevertheless, the overall pattern points toward safer pregnancies in dating markets where women have more leverage in relationships.
Newborns in these more favorable dating markets also appear to benefit. The likelihood of receiving a low APGAR score at birth declines by approximately 8.3% relative to a baseline rate of 2.4%. The APGAR test, performed within the first minutes after birth, quickly assesses heart rate, breathing, muscle tone and reflexes.
Zaremba argues that these changes can be understood through bargaining power. When women have more potential partners, their position within romantic relationships strengthens, potentially allowing them to negotiate safer sexual practices, better allocation of resources and more supportive conditions during pregnancy.
Explaining part of the racial health gap
Using simulations, the study estimates how much of the racial disparity in maternal and infant health might be associated with unequal sex ratios. If Black and White women experienced similar local sex ratios, the model suggests that differences in some outcomes could shrink by 5% to 10%.
According to Zaremba’s calculations, eliminating the 5-percentage-point shortfall of Black men relative to Black women of childbearing age could narrow the Black–White gap in marriage rates among new mothers by around 3.8%. The disparity in chlamydia prevalence could decline by approximately 6%.
The author emphasizes that these effects are modest but meaningful and highlight a largely overlooked social mechanism behind health inequalities. Partner availability does not replace factors such as income, access to healthcare or systemic racism, but it appears to account for a measurable portion of the difference.
Crucially, Zaremba cautions that the study does not directly evaluate criminal justice reforms or other policies that could alter incarceration rates. The results are based on random variation in sex at birth rather than deliberate changes in the number of men living within a community.
Limits of the findings and next questions
The findings are most representative of people living in smaller and medium-sized counties where populations remain relatively stable over time. In large metropolitan areas characterized by greater mobility and wider dating pools, county-level sex ratios may play a smaller role in determining romantic options.
The analysis also assumes that most people date within their own race, age group and county. If substantial numbers regularly travel to find partners or form relationships across racial or age boundaries, local demographic imbalances would have less influence on their bargaining position.
Zaremba emphasizes that his research is descriptive rather than prescriptive. It does not provide dating advice or claim that simply increasing the number of men in a community would automatically improve health. Instead, it illustrates how market conditions can influence private decisions that ultimately become visible in public health data.
Future research, he argues, should examine the mechanisms behind these patterns in greater detail. Important questions include whether women in more favorable dating markets find partners with stronger economic prospects, gain greater influence over household spending or exercise more control over fertility through contraception and abortion.
The research also opens the possibility of investigating men’s outcomes under different dating-market conditions. Researchers could examine whether skewed sex ratios influence men’s mental health, relationship stability or risk-taking behavior, as well as whether some men respond to local imbalances by moving or changing their preferences in partners.
For policymakers, the findings highlight that health is shaped not only by healthcare and insurance coverage but also by the broader social structure of communities. Demographic factors including sex ratios, migration patterns and incarceration can subtly influence the options available in people’s intimate lives and, in turn, their health and the health of their children.
Article prepared by Victoria Caldwell.
