Part One — The Inheritance We Didn’t Choose

The Statistical Trajectory

Statistics

If the first two chapters dismantled the romantic myths — historically, marriage is not eternal; biologically, it is not effortless — then this chapter does something else entirely. It lets the numbers speak. The trends are descriptive rather than ideological, and read carefully they point in a single direction: marriage as a universal life stage is shrinking, as a lifelong commitment is shortening, and as an institution is being redefined.

The question is whether we are willing to face these numbers, or whether we keep our heads buried in the sand of "tradition."

The Long Decline in Marriage Rates

Start with the most basic indicator: the marriage rate. In the United States, the crude marriage rate (marriages per 1,000 population) stood at 12.0 in 1920, dipped during the Great Depression to 7.9 in 1932, and surged after the war — peaking near 16.4 per 1,000 in 1946 — before settling into a long plateau and beginning its sustained decline in the 1970s. By 2019, the rate had fallen to its lowest pre-pandemic level in the roughly century and a half of recorded national data. A slight uptick in recent years looks more like demographic noise than a renewed enthusiasm for marriage.

The picture in Europe is equally stark. The EU's crude marriage rate fell from about 8.0 per 1,000 in 1964 to around 3.9 in the most recent Eurostat releases — a relative decline of more than 50%. The COVID-19 pandemic accelerated the drop, and the recovery has been partial at best.

But raw rates tell only part of the story. The more revealing shift is in household composition. In 1970, married couples made up roughly 70% of American households; in the most recent Census Bureau figures, that share had fallen below half. This is not because Americans stopped living together. It is because cohabitation and solo living replaced marriage.

The Rise of the Unmarried Household

If you assume cohabitation is just "trial marriage," the data will correct you. Among U.S. adults aged 18 to 44, more people have cohabited than have ever married. In the late 1960s, cohabitation was statistically rare — well under 5% of couples sharing a home were unmarried. Today it is common: by recent estimates, around 13% or more of those living with a partner are unmarried, and Pew Research Center reports that a majority of American adults have, by their early 40s, lived with a partner they were not married to. A substantial minority have lived with more than one.

The Netherlands offers a useful European comparison, and it rhymes with the broader drift away from the shared household as the default form of partnership. In recent Statistics Netherlands (CBS) figures, roughly three in ten Dutch adults report no steady partner, and around one in ten describe themselves as in a "lat relationship" (living apart together) — both figures up meaningfully over the past decade. Among those under 25, the majority are single and only a small minority live with a partner.

These are not marginal phenomena. In the Netherlands, they are no longer marginal.

The Stability Gap

Here is where the data becomes uncomfortable for anyone who wants to believe cohabitation is simply marriage by another name.

Cohabiting relationships are, on average, significantly less stable than marriages. The "sliding versus deciding" framework — developed by researchers Scott Stanley and Galena Rhoades — describes couples who drift into shared living without a deliberate commitment decision. Their work, and related studies, finds that couples who cohabit before engagement show higher subsequent divorce risk than those who cohabit after engagement or marry directly. The distinction is not cohabitation itself, but whether it is a deliberate step toward commitment or a convenience that substitutes for it. These findings are correlational — relationship quality and socioeconomic background partly explain the gap — but the pattern is consistent across studies.

Serial cohabitation — three or more cohabiting relationships — is associated with still higher divorce risk and lower reported satisfaction.

The Divorce Plateau

Divorce rates present a more nuanced picture. The U.S. crude divorce rate rose from 1.6 per 1,000 in 1920 to a peak of 5.3 in 1981, then declined to roughly 2.4 by the early 2020s. In the EU, the crude divorce rate roughly doubled from the 1960s to its mid-2000s peak before declining slightly in the most recent figures.

This decline does not mean marriages are getting healthier. Several alternative explanations fit the data better:

The selection effect. Marriage is increasingly concentrated among the educated and affluent — groups with lower divorce rates. Less advantaged couples are more likely to cohabit (and separate) without ever marrying, removing them from the divorce statistics entirely.

The delay effect. People are marrying later, and later marriages are more stable.

The "stickiness" of cohabitation. Many couples who would have divorced in an earlier era never married in the first place. Their separations don't show up in divorce data.

The overall picture is not "more stable marriages." It is a sorting process: stable marriages surviving among the select, while unstable relationships increasingly take non-marital forms that don't register as divorce.

What the Numbers Predict

If current trends continue — and trends are not destiny, as the slight recent upticks remind us — several trajectories become clear:

Marriage will likely become a minority experience. If married-couple households keep declining at recent rates, they could fall below 40% of American households in the coming decade, though a purely linear projection overstates the certainty.
Cohabitation will become the normative first partnership. For younger generations, living together before (or instead of) marriage is already the default. The question is not whether this trend continues, but what legal and social infrastructure will emerge to support it.
The legal gap will become untenable. Cohabiting couples have significantly fewer legal protections than married ones: no automatic inheritance rights, no default medical decision-making, no spousal Social Security or tax benefits. As cohabitation grows, pressure will mount for legal frameworks that recognize these relationships without requiring marriage. Some jurisdictions are already experimenting with cohabitation agreements and registered partnerships.
The "companionate marriage" model will strain further. As Chapter 2 argued, the biological mismatch between attachment and desire doesn't disappear because we wish it would. The couples who survive will be those who adapt their expectations — not to "no expectations," but to different expectations.

The Uncomfortable Conclusion

The statistics don't tell us what we should do. They tell us what is happening. And what is happening is a slow, steady migration away from marriage as the default container for intimate partnership.

This migration is not reducible to a single ideology. It is driven by a convergence of factors: women's economic independence, reliable contraception, longer life spans, declining religious participation, and — as Chapter 2 argued — a biological reality that makes lifelong exclusive passion a difficult goal rather than an effortless one.

The question is not whether this migration is good or bad. The question is whether our legal, social, and cultural institutions will adapt — or whether they will continue to treat marriage as the only legitimate form of committed partnership, leaving a growing share of adults to navigate their relationships without adequate recognition or protection.

The numbers describe the migration. The adaptation is what lags.

The Same Trend, Different Meanings

The numbers so far describe a Western story. The decline they trace is real — but it is not the whole picture, and treating it as universal flattens experiences that do not fit the frame.

In much of East Asia, the same retreat from marriage is underway, but it is experienced and discussed as a demographic emergency rather than a liberation from monopoly. South Korea's total fertility rate fell below 0.8 in 2023 — the lowest in the world, far below replacement. Japan's marriage rate has declined for decades, and the government has framed the trend as an existential threat to the nation, establishing a dedicated minister for children and family policy. China's marriage registrations dropped by more than half over the decade to the early 2020s. In all three, the conversation is not "marriage is a monopoly, let us break it open" — it is "the cost of housing, the impossible demands on women, and the brutal hours of work have made marriage and children unaffordable." The structural causes rhyme with the Western story. The cultural meaning does not. A Korean or Japanese reader may recognize the same economic pressures but experience the decline as loss and crisis, not as the opening of a conversation about alternatives.

In much of the Global South, the picture is different again. Marriage remains near-universal, often early, and in many communities arranged or semi-arranged by family rather than chosen individually. In India, for example, the vast majority of marriages are still arranged, divorce rates are very low — partly by law, partly by social constraint — and cohabitation outside marriage remains statistically marginal and socially fraught. In sub-Saharan Africa, marriage norms vary widely but marriage itself remains a near-universal expectation, often with substantial bridewealth or extended family obligations that shape its meaning in ways Western frameworks do not capture. For a reader in these contexts, the phrase "marriage as a monopoly" may describe an institution that looks nothing like the one they know — or may describe a set of family and community pressures that the Western framing, with its focus on individual choice and romantic partnership, does not name.

The Nordic countries sit at the other end. In Sweden and Norway, cohabitation has been a stable, socially equivalent alternative to marriage for two generations. Couples cohabit, raise children, and separate without the legal precarity that marks the Polish or even the Dutch case. Marriage is not absent — it is simply no longer the threshold for social adulthood or legitimate family formation. It is one option among others. This is the version of the story that comes closest to the "broken monopoly" frame — and it is a version built on a welfare state, strong gender equality, and labor protections that most of the world does not share.

The point is not that one of these is the right story. It is that the Western, professional-class story of marriage as a constraining monopoly to be opted out of is one experience among several — and it is the one this archive is written from. The class dimension, explored in Chapter 10, matters: in the United States and parts of Europe, marriage has become a luxury good for the educated and affluent, a marker of stability that fewer and fewer can access. In East Asia, the decline is felt as a national crisis. In much of the Global South, the institution endures in forms the Western conversation does not always see. A project that claims to open a conversation about the future of intimacy has to be honest about which of these conversations it is actually in — and which ones it is only pointing toward.