Table 1. Effects of time, age and marital status on having one or more casual partners in the past 12 months by gender, 1997–2006.

Explanatory variable	Sample size*	Adjusted odds ratio (95% CI)†	p Value†
Women
Age (years)
13–19	7616 (4.0)	1 (reference)
20–24	3188 (3.9)	1.92 (1.51 to 2.45)	<0.001
25–34	4818 (2.7)	1.54 (1.20 to 1.97)	0.001
35–44	3602 (2.5)	1.23 (0.95 to 1.60)	0.112
45+	6033 (0.8)	0.24 (0.18 to 0.34)	<0.001
Survey year
1997	1677 (1.4)	1 (reference)
1999	2222 (2.5)	2.01 (1.17 to 3.44)	0.012
2000	3398 (3.4)	2.98 (1.78 to 4.97)	<0.001
2001	3599 (3.6)	3.01 (1.82 to 5.00)	<0.001
2003	3535 (2.5)	2.17 (1.29 to 3.64)	0.004
2004	3805 (3.7)	3.25 (1.95 to 5.42)	<0.001
2005	3562 (2.6)	2.25 (1.33 to 3.81)	0.002
2006	3464 (1.4)	1.27 (0.73 to 2.23)	0.393
Marital status
Unmarried	13505 (4.1)	1 (reference)
Married	11085 (1.1)	0.19 (0.15 to 0.24)	<0.001
Men
Age (years)
13–19	8055 (8.2)	1 (reference)
20–24	2241 (25.8)	4.65 (4.03 to 5.37)	<0.001
25–34	3412 (20.4)	4.66 (3.97 to 5.48)	<0.001
35–44	2514 (13.3)	2.99 (2.45 to 3.64)	<0.001
45+	4943 (4.0)	0.74 (0.60 to 0.92)	0.006
Survey year
1997	1573 (11.6)	1 (reference)
1999	2026 (11.1)	1.03 (0.81 to 1.30)	0.818
2000	2857 (12.4)	1.23 (0.99 to 1.52)	0.065
2001	3139 (12.6)	1.25 (1.01 to 1.54)	0.041
2003	2959 (11.6)	1.19 (0.96 to 1.48)	0.117
2004	3105 (12.7)	1.35 (1.10 to 1.68)	0.005
2005	2774 (10.7)	1.13 (0.90 to 1.41)	0.284
2006	2735 (10.2)	1.06 (0.85 to 1.33)	0.585
Marital status
Unmarried	12579 (12.7)	1 (reference)
Married	8031 (9.4)	0.47 (0.41 to 0.54)	<0.001

*Values in parentheses are the percentage with ⩾1 casual partners.

†Adjusted odds ratio adjusts for the factors in the models other than the one in consideration (four categorical age variables, seven year variables and one categorical variable for marital status).

‡Logistic regression Wald test with Huber correction.