Year	Percent
1990	88.38
1991	88.35
1992	88.53
1993	88.35
1994	88.55
1995	88.33
1996	88.31
1997	88.37
1998	88.43
1999	87.17
2000	85.77
2001	84.29
2002	82.67
2003	80.92
2004	79.02
2005	76.98
2006	74.91
2007	72.71
2008	70.39
2009	67.96
2010	65.41
2011	62.86
2012	60.23
2013	57.53
2014	57.39
2015	57.27
2016	57.16
2017	57.03
2018	56.9
2019	56.73