Year	Percent
1997	97.63538
1998	95.77996
1999	95.38868
2000	95.05081
2001	96.41726
2002	96.60085
2003	95.52335
2004	95.16371
2005	95.59976
2006	95.74006
2007	95.40534
2008	95.91734
2009	95.10816
2010	95.06767
2011	95.19269
2012	95.19959
2013	94.40201
2014	94.58099
2015	93.7825
2016	93.70618
2017	93.9012