Year	% of cohort
1997	77.5167999267578
1998	77.8414306640625
1999	77.7020034790039
2000	76.3235015869141
2001	75.1013107299805
2002	74.3043823242188
2003	73.2347564697266
2004	72.522346496582
2005	73.5198516845703
2006	62.4954299926758
2007	61.1829605102539
2008	72.4151077270508
2009	67.4469909667969
2010	63.8848304748535
2011	68.1202163696289
2012	68.5811004638672
2013	75.0376968383789
2014	74.6400833129883
2015	73.8017730712891
2016	71.4922714233398
2017	70.1998519897461
2018	69.5553512573242
2019	69.7071990966797