Table 2.

Descriptive statistics of district networks and students by wave

Variable	Wave	Overall	District 1	District 2	District 3	District 4	District 5	District 6	District 7
No. of participants	W1	1,170	91	80	104	96	87	355	357
	W2	1,186	92	84	106	96	87	350	371
	W3	1,166	91	83	106	96	83	351	356
Density: No. of outgoing friend nominations as % of max. possible	W1	23%	22%	24%	26%	17%	25%	28%	17%
	W2	16%	14%	14%	16%	14%	17%	21%	12%
	W3	13%	17%	14%	15%	12%	8%	18%	9%
% reciprocated ties (ego and alter mutually choose each other)	W1	33%	43%	41%	41%	24%	37%	34%	22%
	W2	31%	44%	17%	36%	31%	44%	32%	23%
	W3	30%	39%	26%	34%	32%	21%	33%	21%
Average outdegree (no. of outgoing friendship nominations)	W1	2.35	2.18	2.41	2.60	1.68	2.43	2.80	1.68
	W2	1.61	1.42	1.40	1.50	1.33	1.63	2.00	1.20
	W3	1.39	1.63	1.37	1.43	1.08	0.76	1.72	0.89
Jaccard indices: Change in ties from previous wavea	W1	–	–	–	–	–	–	–	–
	W2	–	0.29	0.23	0.30	0.18	0.26	0.23	0.19
	W3	–	0.25	0.25	0.31	0.20	0.18	0.22	0.20
% of participants who have ever had a heavy drinking episode	W1	15%	9%	22%	16%	17%	26%	14%	12%
	W2	24%	19%	30%	24%	27%	35%	24%	23%
	W3	33%	24%	43%	32%	35%	44%	30%	32%
Median no. of days (of last 30) spent unsupervised time with friends	W1	3.0	2.0	3.0	2.0	2.0	1.0	3.0	2.0
	W2	2.0	2.0	3.0	1.0	2.0	1.0	3.0	3.0
	W3	2.0	1.0	3.0	2.0	2.0	2.0	2.0	3.0
% isolates (no outgoing or incoming ties)	W1	10%	11%	10%	9%	14%	7%	7%	13%
	W2	18%	14%	17%	22%	19%	15%	13%	23%
	W3	21%	15%	18%	16%	20%	33%	13%	30%

Notes: No. = number; W = wave; max. = maximum.

^aThe Jaccard index is a measure of change in ties in relation to total number of ties that could have changed.