Table1

Follow-up among study participants

			Non-returning participants
Description	Total cohort	Returning participants	N	Percent
2000 to 2001–2013	11 201	11 201	0	0.00
2000–2001 to 2002–2013	12 363	12 260	103	0.83
2000–2002 to 2003–2013	13 474	13 291	183	1.36
2000–2003 to 2004–2013	15 849	15 212	637	4.02
2000–2005 to 2006–2013	16 614	15 637	977	5.88
2000–2006 to 2007–2013	17 136	15 838	1298	7.57
2000–2007 to 2008–2013	17 963	16 263	1700	9.46
2000–2008 to 2009–2013	18 947	16 833	2114	11.16
2000–2009 to 2010–2013	20 221	17 476	2745	13.57
2000–2010 to 2011–2013	22 128	18 848	3280	14.82
2000–2011 to 2012–2013	22 670	18 775	3895	17.18
2000–2012 to 2013	24 636	18 521	6115	24.82