Year	% of cohort
1997	79.6216430664062
1998	79.9529037475586
1999	79.7557601928711
2000	78.1518325805664
2001	76.5741806030273
2002	75.7247467041016
2003	74.3614730834961
2004	73.6325607299805
2005	75.4034881591797
2006	63.2053985595703
2007	60.7433586120605
2008	72.0489883422852
2009	67.3126831054688
2010	64.476188659668
2011	69.2188110351562
2012	69.0454864501953
2013	74.0593795776367
2014	74.2054595947266
2015	73.7345275878906
2016	71.1217803955078
2017	69.5626525878906
2018	72.7611083984375
2019	72.9034423828125