1. Demographic and social characteristics of studies included in meta‐analyses (%).

1st Author	Mean/median age, years	Male	Non‐owner occupier	Single parents	BME group	Unemployment
Yorkston 2007	‐	51	‐	‐	9	‐
Zhao 2006	‐	‐	‐	‐	‐	‐
Phelan 2010	0 (prenatal mothers)	46	‐	18	30	17
Bulzachelli 2009	2.5	53	‐	70	96	53
Sangvai 2007	‐	‐	‐	‐	48	‐
Swart 2008	‐	‐	‐	52	‐	67
Kendrick 2010	‐	‐	100	70	8	65
Nansel 2008	1.2	52	71	32	66	‐
Kendrick 2007	8.7	52	‐	‐	‐	‐
Hwang 2006	‐	‐	‐	‐	‐	‐
Gittelman 2007	‐	‐	‐	‐	84	‐
Gielen 2007	‐	50	‐	69	93	48
Carman 2006	‐	‐	‐	‐	‐	‐
Babul 2007	1	52	39	11	‐	‐
Dershewitz 1977	‐	‐	‐	0	‐	81
Baudier 1988	‐	‐	‐	‐	‐	‐
Campbell 2001	13	51	‐	‐	‐	‐
Kendrick 2005	0.75	‐	20	5	4	‐
McDonald 2005	0.81	48	83	54	93	‐
Watson 2005	2.15	51	46	28	15	70
Posner 2004	2.26	57	55	‐	84	34
Kelly 2003	‐	‐	‐	13	93	‐
Sznajder 2003	1.36 (youngest child)	‐	‐	13	‐	34
DiGuiseppi 2002 (smoke alarm ownership data only)	‐	‐	100	13	18	‐
Gielen 2002	0.25	‐	‐	87	94	77
Hendrickson 2005	2	62	‐	27	88	74
Nansel 2002	0.95	48	73	19	95	‐
King 2001	2	59	‐	‐	‐	‐
Johnston 2000	4.5	53	‐	56	30	57
Clamp 1998	2.59	‐	21	10	1	12
Waller 1993	2	‐	‐	‐	‐	‐
Woolf 1992	1.92	‐	‐	11	10	‐
Katcher 1989	8.5	‐	‐	‐	3	‐
Barone 1988	‐	‐	‐	‐	‐	‐
Williams 1998	‐	‐	‐	‐	‐	‐
Matthews 1988	‐	‐	‐	‐	‐	‐
Davis 1987	9	‐	‐	‐	‐	‐
Kelly 1987	0.5	‐	89	81	95	‐
Woolf 1987	‐	‐	‐	42	56	56 (maternal)
Thomas 1984	‐	‐	‐	‐	‐	‐
Kendrick 1999	0.67	52	33	12	7	11
Fergusson 1982	2	‐	‐	9	7	‐
Miller 1982	‐	‐	13	‐	‐	‐
Tan 2004	0.75	‐	79	‐	‐	‐
Georgieff 2004	1.5	‐	‐	25	2	‐
Mock 2003	6	‐	‐	‐	‐	‐
Lindquist 1998, 1999, 2001, 2002, 2004	‐	‐	‐	‐	‐	‐
Ytterstad 1995, 1998	2	‐	‐	‐	‐	‐
Petridou 1997	9.5	‐	‐	4	‐	‐
Bentzen 1997	‐	‐	‐	‐	‐	‐
Svanstrom 1995	‐	‐	‐	‐	‐	‐
Schwarz 1993	‐	‐	‐	‐	96	‐
Guyer 1989, 1991	‐	‐	48	‐	8	‐
Jenkins 1996	‐	63	‐	28	48	22 (paternal)