Year	Percent
1990	68.89
1991	69.16
1992	69.37
1993	69.53
1994	69
1995	68.49
1996	68.16
1997	67.85
1998	67.56
1999	67.26
2000	66.94
2001	66.44
2002	65.95
2003	66.08
2004	66.2
2005	66.29
2006	66.38
2007	66.43
2008	66.46
2009	66.49
2010	66.52
2011	66.5
2012	66.49
2013	66.49
2014	66.48
2015	66.44
2016	66.38
2017	66.3
2018	66.2
2019	66.46