Year	% of cohort
1997	98.1226196289062
1998	97.9685592651367
2001	98.1138687133789
2002	97.3295211791992
2003	97.0465316772461
2004	98.4558334350586
2005	96.6344909667969
2009	97.4425735473633
2010	97.3080596923828
2011	96.8733901977539
2012	97.4719161987305
2013	99.4088668823242
2014	97.6418075561523
2015	99.0731887817383
2016	98.6014709472656
2019	99.5556030273438