Table 1. Characteristics of never smokers, current non-smokers, intermittent smokers, and daily smokers among Korean adolescents.

		Total	Never smokers	Current non-smokers	Intermittent smokers	Daily smokers
		% (N)
Gender	Male	51.0 (29,492)	45.8 (19,411)	59.7 (5,090)	67.6 (2,279)	75.6 (2,712)
	Female	49.0 (28,365)	54.2 (22,962)	40.3 (3,433)	32.4 (1,094)	24.4 (876)
Paternal education	< = Middle school	7.7 (4,460)	6.8 (2,900)	9.7 (827)	9.0 (305)	11.9 (428)
	= High school	44.6 (25,825)	43.0 (18,227)	48.0 (4,095)	49.0 (1,653)	51.6 (1,850)
	> = College	47.6 (27,572)	50.1 (21,246)	42.3 (3,601)	42.0 (1,415)	36.5 (1,310)
Maternal education	< = Middle school	7.7 (4,430)	6.9 (2,931)	9.2 (786)	8.8 (298)	11.6 (415)
	= High school	57.9 (33,513)	56.8 (24,072)	60.6 (5,166)	61.0 (2,057)	61.8 (2,218)
	> = College	34.4 (19,914)	36.3 (15,370)	30.2 (2,571)	30.2 (1,018)	26.6 (955)
Substance use	Never	99.6 (57,634)	99.8 (42,306)	99.5 (8,480)	98.8 (3,331)	98.0 (3,517)
	Past use	0.2 (139)	0.1 (43)	0.4 (32)	1.0 (34)	0.8 (30)
	Current use	0.1 (86)	0.1 (26)	0.1 (11)	0.2 (8)	1.1 (41)
Depressive symptoms	Yes	38.0 (21,982)	34.7 (14,686)	44.7 (3,813)	48.3 (1,629)	51.7 (1,854)
	No	62.0 (35,875)	65.3 (27,687)	55.3 (4,710)	51.7 (1,744)	48.3 (1,734)
		Range	Mean (SD)
School grade		1–6	3.47 (1.70)	3.76 (1.61)	3.72 (1.54)	4.67 (1.23)
Self-rated academic achievement		1–5	3.20 (1.15)	2.85 (1.18)	2.64 (1.17)	2.34 (1.17)
Weekly allowance		1–16	2.72 (2.41)	3.26 (2.86)	3.81 (3.40)	4.86 (4.10)
Family Affluent Scale (FAS)		4–13	8.71 (1.78)	8.64 (1.80)	8.77 (1.82)	8.60 (1.83)
Secondhand smoking at home		0–7	1.31 (2.17)	1.75 (2.49)	2.00 (2.48)	2.65 (3.00)
Alcohol Use		0–7	0.23 (0.73)	0.61 (1.2)	1.47 (1.63)	2.52 (1.85)
Stress status		1–5	3.34 (0.93)	3.46 (0.96)	3.54 (0.96)	3.59 (1.00)