Year	Percent
1997	92.05646
1998	91.02763
1999	90.32632
2000	90.04605
2001	89.67123
2002	89.55952
2003	88.36672
2004	88.98776
2005	89.67516
2006	89.19864
2007	89.46049
2008	89.48212
2009	88.66955
2010	87.91869
2011	87.30577
2012	86.67165
2013	86.58632
2014	87.34608
2015	87.31735
2016	86.86958
2017	87.27434