A proposed U.S. transportation rule published in the Federal Register this month would allow some major transit projects to receive a larger federal funding share when the birth and marriage rates in the project corridor meet specified thresholds. The proposed formula could add as much as ten percentage points when both demographic criteria are satisfied. It is a proposal, not a rule already in force.
The policy is unusual because it places fertility and marriage inside a program normally evaluated through transportation criteria. It also exposes a broader change in the way governments are thinking about low birth rates. Housing, tax policy, childcare, labor rules and now even infrastructure can be drawn into a single national objective: produce conditions in which more people marry and have children.
The demographic concern is real. In 2024, the European Union’s total fertility rate fell to 1.34 children per woman, the lowest EU figure in the comparable series. South Korea’s preliminary 2025 total fertility rate rose to 0.80 after reaching 0.72 in 2023, but it remained far below the roughly 2.1 replacement benchmark used for low-mortality populations.
The policy difficulty is that one fertility rate can conceal two different problems.
Some people want more children than they expect to have. Others increasingly prefer smaller families, later parenthood or no children. Helping the first group and persuading the second group to change their preferences are not the same public project.
Many people still face barriers to the families they want
Low fertility is sometimes explained as if younger adults have simply rejected parenthood. The evidence is more complicated.
UNFPA’s 2026 Demographic Futures Survey collected responses from more than 108,000 internet-connected adults aged 18 to 39 across 73 countries. The organization explicitly warns that the results are not nationally representative and should not be interpreted as population-level estimates.
Within that surveyed group, two children remained the most commonly reported ideal family size in five of seven regional groupings. Financial security was identified as an important condition for parenthood by 88 percent of respondents, stable employment by 87 percent and emotional readiness by 85 percent.
A separate UNFPA survey published in 2025 also found a substantial gap between desired and expected family size in its 14-country sample, with respondents citing the cost of parenthood, job insecurity, housing, uncertainty about the future and the absence of a suitable partner among the barriers.
These results point to a genuine policy problem. A person who wants a second child but cannot afford childcare faces a different situation from a person who has decided that one child is enough. Housing supply, childcare, parental leave, employment security, fertility treatment and the division of care work can reduce the first kind of constraint.
OECD research on Denmark supports a cautious version of that argument. Affordable childcare and policies that make employment and family life more compatible can reduce barriers to parenthood, while simple cash transfers tend to have only modest fertility effects that are often temporary.
Helping people achieve family plans is therefore a reasonable policy objective even when the national fertility rate does not return to a particular target.
Preferences are changing as well
Economic constraints do not explain the entire decline.
A review published in the September 2026 issue of the peer-reviewed Journal of Economic Literature concludes that fertility decline in high-income countries reflects a complex mixture of economic conditions, changing social norms, work, gender roles, leisure and an expanded range of possible adult lives. The authors describe parenthood as becoming less central to the way some cohorts define a fulfilling life.
An NBER working paper published in August finds a similar change in survey data. Across the countries and years studied, the average reported ideal number of children fell from 2.42 in 2012 to 2.31 in 2022, while the share of respondents intending to have a child within three years fell from 28 percent to 21 percent over a similar period. The authors connect part of the change to attitudes about personal freedom, women’s work and whether children are necessary for a fulfilling life.
Because the NBER paper is a working paper, its estimates should not be treated as settled consensus. The broader peer-reviewed literature nevertheless supports the idea that fertility reflects preferences as well as constraints.
This creates a second policy question. A government may want enough births to stabilize its population structure, tax base or future workforce. Adults are deciding how to organize their own relationships, careers and time. Those two calculations do not have to produce the same number.
Replacement fertility is a demographic benchmark. It is not a statement about how many children an individual should want.
Denmark shows why family policy and fertility targets should be separated
Denmark provides a useful example because it combines extensive family support with fertility well below replacement.
Children have access to heavily subsidized childcare, parental leave is extensive by international standards, and family benefits reduce part of the cost of raising children. Statistics Denmark reports a 2025 total fertility rate of 1.506 children per woman.
That number does not prove that Danish family policy failed.
Without childcare and parental leave, fertility could have been lower. The same programs also support women’s employment, household income, children’s welfare and parents’ quality of life. A policy can be socially successful even if it does not push the national fertility rate back to 2.1.
This is a counterfactual problem that is often lost in public debate. We rarely observe what fertility would have been in the same country without the policy package.
South Korea supplies the opposite caution. Its official preliminary data show the total fertility rate rising from 0.72 in 2023 to 0.75 in 2024 and 0.80 in 2025. The rebound demonstrates that fertility can move. It does not identify one policy as the cause or show that the country has found a reliable route back to replacement level.
Policies, marriage patterns, economic conditions and population structure can all move at the same time.
A single national fertility rate cannot separate them by itself.
The two gaps overlap, but they should not be confused
The distinction between unrealized family plans and changing family preferences is not perfectly clean.
Preferences themselves are shaped by experience. Someone who sees parents struggling with expensive housing, long working hours and unequal care responsibilities may eventually decide that one child is ideal because two no longer seem realistic. Better family policy can therefore change both what people are able to do and, over time, what they imagine as desirable.
The point is not to place everyone into two fixed categories.
It is to prevent governments from assuming that removing financial barriers will automatically restore replacement fertility.
Closing the gap between the family people want and the family they can achieve may raise fertility and improve welfare. It still does not logically guarantee that the sum of individual choices will meet a national demographic target.
Once that is understood, success can be measured more honestly.
A childcare policy can be valuable because it reduces the career penalty of parenthood even if total fertility remains low. Fertility treatment can matter because it allows people to realize reproductive intentions even if the effect on the national birth rate is small. Housing reform can improve family formation without turning every housing decision into pronatalist policy.
Low fertility may need to be adapted to as well as reversed
Governments have strong reasons to care about sustained low fertility. Aging populations change pension systems, health and long-term-care spending, labor supply and the ratio of workers to retirees.
The time horizon creates a constraint that fertility policy alone cannot solve. A child born because of a policy introduced today will not enter the labor force for roughly two decades.
This is why policies aimed at supporting families need to coexist with adaptation. Longer working lives, higher employment among underrepresented groups, productivity growth and, where societies choose it, immigration can all affect the economic consequences of aging sooner than a change in today’s birth rate.
That approach is less dramatic than promising to reverse demographic decline. It is also more realistic about what governments control.
States can reduce unnecessary barriers that prevent people from having the families they want. They can make parenthood less damaging to income and careers. They can plan pension systems, labor markets and public services for the population that actually emerges.
What they cannot assume is that those policies will produce exactly the number of births required by a demographic model.
Low fertility can reflect constrained choice and changing choice at the same time. A serious fertility policy has to know which problem it is trying to solve.
Sources
- U.S. Federal Transit Administration — Proposed Capital Investment Grants policy guidance, Federal Register 2026-20179
- Eurostat — EU fertility rate at 1.34 live births per woman in 2024
- South Korea Ministry of Data and Statistics — Preliminary Results of Birth and Death Statistics in 2025
- UNFPA — Demographic Futures Survey 2026
- UNFPA — State of World Population 2025 / fertility barriers
- American Economic Association — Why Is Fertility So Low in High-Income Countries?
- NBER — Falling Fertility: The Changing Value of Freedom, Fulfillment, and Family
- OECD — Reducing barriers to family formation in Denmark
- Statistics Denmark — Fertility