In 2001, men and women aged 16 to 59 were asked details about past cohabitations which did not end in marriage. These questions were first asked in 2000, while the number of such cohabitations had previously been asked in 1998. These periods of completed cohabitation did not include the current relationship of a respondent living as a couple at the time of interview. With the exception of those who chose the self-completion option, the majority of married and cohabiting respondents were interviewed in the presence of their partner; it is therefore possible that, for these groups, there was some under-reporting of previous cohabitations.

Among adults aged 16 to 59 in 2001:

• 13% reported at least one such cohabiting union that did not end in marriage;
• 10% had one of these relationships, 2% two and 1% three or more;

• there was no statistically significant difference between the proportions of men and women reporting at least one completed cohabitation not ending in marriage (14% of men and 13% of women);
• the highest proportions reporting at least one such relationship were found to be adults aged 25 to 39 (between 19% and 22%). This compares with between 5% and 9% of adults aged 45 to 59.