Year	% of cohort
2006	99.9509429931641
2007	96.9523468017578
2008	94.7740478515625
2009	92.7105407714844
2010	92.1730804443359
2011	93.4914932250977
2012	97.8552322387695
2013	97.4645614624023
2016	98.7591400146484