Marriage held a near-monopoly on American partnership for most of the 20th century. Two people met, dated for a socially appropriate stretch, got engaged, and signed a license. That sequence still happens, but it now competes with a growing list of alternatives that would have raised eyebrows a generation ago.

Cohabitation without a ring, polyamorous triads, open partnerships with negotiated boundaries, and long-distance arrangements sustained entirely through screens all occupy real space in how Americans pair up. The numbers confirm what anecdotal observation has been suggesting for years: a single template for romantic life no longer holds.

The Marriage Rate Tells a Complicated Story

At first glance, marriage looks stable. Pew Research Center published an analysis of Census Bureau data in January 2025 showing the married share of U.S. adults inched from 50% to 51% between 2019 and 2023. That looks like a vote of confidence in the institution until you read the fine print. The uptick is not coming from new couples rushing to the altar.

It is coming from fewer people leaving marriages they are already in. In 2023, a record-low 1.4% of married adults divorced, down from a peak of 2.0% in 2012. Existing marriages are lasting longer, but fewer people are entering new ones.

Meanwhile, the share of adults living with an unmarried partner went from 6% to 7% over the same period. That may seem small in isolation, but Penn Wharton Budget Model projections from February 2025 put cohabitation on a steep upward curve, estimating it will pass 16% by 2040.

The married share, by that same model, falls below 40%. People are not abandoning partnership. They are doing it without the paperwork.

Relationship Preferences

People are forming partnerships on their own terms, and the variety keeps growing. Some are looking for sugar babies, others are exploring polyamory, and many are cohabiting without any plan to marry.

A February 2025 Penn Wharton Budget Model projection estimates cohabitation rates will climb past 16% by 2040, while the married share falls below 40%. These aren’t fringe experiments anymore.

An April 2025 YouGov survey of 1,125 U.S. adults found that 9% have been in a polyamorous or open relationship, and 58% of those open to it said they wanted different needs fulfilled. Gallup’s 2025 Values and Beliefs poll recorded 21% of Americans calling polygamy morally acceptable, up from 6% in 2005.

Who Is Actually Practicing Non-Monogamy

Peer-reviewed research published through PubMed Central estimates that between 3% and 7% of adults are in a consensual non-monogamy partnership at any given time, and up to 25% have tried one at some point. Those are not trivial numbers.

OPEN’s 2025 Community Survey, conducted as formal academic research in partnership with Dr. Amy Moors of Chapman University, collected nearly 6,000 responses from non-monogamous people across 65 countries. The survey represents one of the largest data sets on this population to date.

It suggests that people practicing non-monogamy are building organized communities, sharing terminology, and developing internal norms around consent and disclosure that run parallel to mainstream dating culture.

Among younger adults, acceptance runs higher. Gallup found that 31% of Americans aged 18 to 34 consider polygamy morally acceptable, compared to 21% across all age groups. This generational gap is worth noting because attitudes at younger ages tend to carry forward.

Why People Are Choosing Differently

The YouGov data points to something practical. Among respondents open to polyamory or open partnerships, 58% said they wanted different needs fulfilled. That answer is blunt and revealing. It suggests these choices are less about ideology and more about recognizing that 1 person may not cover everything someone wants from a romantic and sexual life.

The Institutions Are Slow to Catch Up

Legal systems, tax codes, health insurance policies, and custody frameworks are all built around a 2-person married unit.

When someone is in a polyamorous triad or a long-term cohabiting partnership, they often lack the legal protections that married couples receive automatically. Hospital visitation, inheritance, parental rights, and tax filing all default to structures that assume marriage.

Some municipalities have started recognizing domestic partnerships or multi-partner agreements, but those remain rare. The gap between how people actually live and how the law treats their arrangements is wide and growing wider.

What Comes Next Is Already Happening

The projections from Penn Wharton suggest that by 2040 the married population will be a minority of American adults. That does not mean partnership is declining. It means the forms partnership takes are multiplying.

Cohabitation, consensual non-monogamy, sugar dating, and other configurations are absorbing people who in previous generations would have married by default or remained alone.

The old playbook assumed everyone wanted the same thing. The data says otherwise, and the trend lines are heading in 1 direction.