The Office for National Statistics (ONS) has reported that the number of families that include a couple in a legally registered partnership in the UK has increased by 3.7% in the past decade, to 12.7 million.
However, the number of cohabiting couple families saw an increase of 22.9% over the same period, to 3.6 million.
Meanwhile, the number of people living alone in the UK has increased by 8.3% over the last 10 years.
52% of single retired people earn more than they spend, compared to 78% for couples.
Helen Morrissey, senior pensions and retirement analyst at Hargreaves Lansdown, said: “The UK’s living patterns continue to shift, with the number of people choosing to cohabit soaring over the past decade. Some of these couples will go on to marry but others will have no intention of doing so. We’re also seeing the number of people living alone continuing to grow strongly and, in places like London, one person households account for more than a quarter of all households.
“These shifts turn traditional financial planning on its head. A cohabiting couple has different rights to one that is married or in a civil partnership, while a single person needs to make further provision to secure their financial resilience, and this can cause challenges.”