Year	% of cohort
1998	96.7313003540039
1999	96.7294998168945
2000	95.5151901245117
2001	98.8349380493164
2002	98.7586288452148
2003	98.8256301879883
2004	97.9790115356445
2005	99.3951034545898
2006	98.986701965332
2007	99.2403106689453
2008	98.6815032958984
2009	98.8599014282227
2010	98.9157867431641
2011	97.9880065917969
2013	98.3737716674805
2014	98.6179504394531
2015	99.0834121704102
2016	98.9567794799805