Year	% of cohort
1999	96.7097778320312
2000	95.9051818847656
2001	95.3323211669922
2002	94.8461303710938
2003	94.9200897216797
2004	93.99658203125
2005	94.9393310546875
2006	94.3852996826172
2007	88.1978912353516
2008	93.0412292480469
2009	93.4448394775391
2013	96.0028076171875