Table 1.

Sample size and student response rate by year

Year	NZ Year 10 population	Valid survey responses*	Valid survey responses that met all study inclusion criteria	Proportion of Year-10 population that met all study inclusion criteria (%)
2002	58 812	29 173	28 088	50
2003	61 028	32 705	31 377	54
2004	62 852	31 630	30 807	46
2005	64 619	32 561	31 833	51
2006	63 086	32 844	31 690	52
2007	62 012	25 978	25 109	42
2008	61 485	30 903	29 682	50
2009	61 355	25 757	24 755	42
2010	61 210	32 832	31 696	54
2011	59 562	26 856	26 028	45
2012	59 627	31 983	30 396	43
2013	57 929	28 340	27 014	49
2014	59 612	31 125	29 303	47
2015	59 528	21 567	20 443	36
Total	852 717	414 254	398 221	47

*Valid survey responses=those with complete data for age (14 or 15), sex, ethnicity and smoking status.

NZ, New Zealand.