For questions on duration of cohabitation, respondents were asked how long each completed cohabitation had lasted and give either the start date or the end date. The date which had not been given was then calculated and checked with the respondent, who could disagree and correct it. Length of cohabitation was based on the corrected dates where required.

First previous cohabitations which did not end in marriage tended to be longer than second such cohabitations.

• The mean length of time for first cohabitations which did not end in marriage was 39 months compared with 28 months for second cohabitations.
• Among people aged 16 to 59, around 42% of first cohabitations lasted for less than 2 years compared with 57% of second cohabitations.

First cohabitations which were the only past cohabitation tended to be longer than those which were the first of two or more among people aged 16 to 59.

• The mean length of a first and only completed cohabitation was 40 months compared with a mean length of 34 months for a cohabitation which was the first of two or more.
• Differences were more more marked among women with a mean length of a first and only completed cohabitation of 44 months compared with 35 months for a cohabitation which was the first of two or more.