Two trends are running in parallel across most Western societies: marriage rates are declining, and ethical non-monogamy is becoming more visible and more widely practised. These are often presented as a single story about the breakdown of traditional relationships. The actual relationship between them is more interesting and less tidy than that framing suggests.
What's driving the marriage decline
Marriage rates in most Western countries have been falling for decades, with the trend accelerating among younger cohorts. The reasons are multiple and intersecting: people are delaying marriage until later in life; a significant share of adults who would previously have married are choosing long-term partnerships without legal marriage; rising housing costs and economic instability make the financial merging that marriage historically implied harder to arrange; and the cultural assumption that adult life should culminate in marriage has simply weakened.
Most of the people driving declining marriage rates are not practising CNM. They are single for longer, in long-term monogamous partnerships they haven't formalised, or in a period of relationship life that doesn't include a stable partner. The marriage decline is primarily a story about monogamy changing, not about non-monogamy spreading.
Where CNM and declining marriage intersect
The structural conditions that produce declining marriage also make CNM more available as a choice. When monogamous marriage is no longer automatically presumed as the endpoint of adult life, the space for alternative structures grows. People who might have felt that they had to choose between monogamous marriage and no stable partnership now have a wider visible range of options, including various CNM structures.
The cultural shift also matters. A generation that grew up with marriage as a less automatic assumption, and with visible discussions of alternative relationship structures, enters adulthood with a different relationship to what's possible. This doesn't mean they become CNM practitioners — most don't — but it means CNM is more likely to be an active choice they've considered rather than something that simply didn't occur to them.
What they don't share
CNM practitioners and people who don't marry are not interchangeable populations. People who don't marry are a very large and heterogeneous group: many are in conventional monogamous relationships that happen not to be legally formalised. CNM practitioners are a smaller, more specific group who've made active choices about relationship structure that go beyond marriage/no-marriage.
The decline of marriage is also partly a story about people having less relationship infrastructure overall — fewer stable long-term partnerships, more time spent single, more relationship instability in younger adulthood. This isn't what CNM describes. CNM involves more relational investment, not less: more relationships to maintain, more communication, more active negotiation of terms.
The misreading this creates
When CNM and declining marriage are treated as the same phenomenon, it produces a mischaracterisation of CNM as a form of relationship avoidance or commitment-phobia. This is the wrong reading. CNM practitioners are typically more relationship-focused than the average person avoiding marriage, not less. The commitment in CNM is distributed differently — across multiple relationships rather than concentrated in a single legal partnership — but it's generally substantial.
The more accurate framing is that both trends reflect a cultural loosening of the assumption that adult life has one correct relationship structure. Marriage, long-term monogamous cohabitation without marriage, various CNM configurations, extended singlehood, and other arrangements are all becoming more equally available as genuine options rather than deviations from a norm. CNM is one part of that broader diversification, not a symptom of relationship abandonment.