Year	% of cohort
1997	98.2277297973633
1998	97.9685592651367
1999	98.7303009033203
2000	98.1060562133789
2001	98.1948318481445
2002	98.7621612548828
2003	97.7257690429688
2004	98.70166015625
2005	96.9667129516602
2007	99.4200897216797
2008	99.4280471801758
2009	97.4425735473633
2010	97.9284210205078
2011	97.7809677124023
2012	97.8936309814453
2013	99.5794677734375
2014	97.7902908325195
2015	99.0731887817383
2016	98.8678436279297
2017	99.9391174316406
2018	98.9663314819336
2019	99.5556030273438