Table 1. Proportion Using Substances by Wave and School-Level Descriptive Statistics.

Individual Characteristics	N	Mean	SD	Min.	Max.
Gender	55,084
Male		0.480	--	0	1
Female		0.520	--	0	1
Race	55,044
White		0.530	--	0	1
Black		0.219	--	0	1
Hispanic		0.160	--	0	1
Asian		0.075	--	0	1
Other		0.015	--	0	1
Parental Education	47,316
<HS		0.113	--	0	1
HS		0.244	--	0	1
Some College		0.306	--	0	1
BA+		0.337	--	0	1
CES-D	55,016	10.9	7.45	0	56
Delinquency Scale	54,820	4.12	5.03	0	45
Age by Wave
Wave 1	13,765	15.2	1.65	13	20
Wave 2	9,702	16.2	1.57	13	21
Wave 3	10,239	21.9	1.70	18	27
Wave 4	10,600	28.4	1.70	24	31
5HTTLPR	44,941
L′/L′		0.237	--	0	1
S′/L′		0.482	--	0	1
S′/S′		0.280	--	0	1
School Variables	N	Mean	SD	Min.	Max.
School Mean Tobacco Use	133
Any Use		35.4	8.2	5.6	53.6
Heavy Use		10.4	4.9	0.0	25.7
School Mean Alcohol Use	133
Any Use		53.9	9.5	12.0	72.9
Heavy Use		10.8	3.9	0.0	22.9
School Excess Proportion (EP)	133
Any Use		9.08	2.5	1.2	15.6
Heavy Use		2.75	1.2	-0.2	8.3
School Proportion Co-Users (PC)	129
Any Use		29.0	7.5	5.6	49.9
Heavy Use		4.02	1.9	0.0	14.2

Note: All school variable values are multiplied by 100, here and in regression models. The analytical sample includes 13,773 individuals, observed across four in-home waves of the Add Health dataset. Sample sizes for individual characteristics reflect pooled person*wave observations (with the exception of age by wave). Sample sizes for schools are the number of discrete schools, and descriptive statistics are calculated at the school level.