Year	Percent
1991	89.17287
1992	89.03308
1993	88.96616
1994	88.99846
1995	89.08535
1996	88.92277
1997	88.80304
1998	88.76654
1999	88.74499
2000	88.55561
2001	88.23922
2002	87.70888
2003	87.01938
2004	86.14208
2005	85.16441
2006	84.13501
2007	83.08785
2008	81.86957
2009	80.71406
2010	79.45007
2011	78.08631
2012	76.60916
2013	72.90198
2014	68.45258
2015	66.94717
2016	65.81883
2017	64.6177
2018	63.34442
2019	62.29604