Table 1.

Data collection waves

	N	Year of data collection	Mean age (±SD)	Male/female (%)
1st wave	662	2011–2012	18 ± 1.5 years	50.2/49.8
2nd wave	606	2014	22 ± 5.6 years	36.6/63.4
3rd wave	1,139	2014	21 ± 2.0 years	43.3/56.7
4th wave	596	2015	22 ± 1.9 years	39.1/60.9
Total	3,003		21 ± 2.8 years	42.6/57.4