Year	Percent
1990	66.6
1991	66.76
1992	67
1993	67.3
1994	67.61
1995	67.87
1996	67.93
1997	68.08
1998	68.05
1999	67.68
2000	67.82
2001	67.92
2002	67.91
2003	68.48
2004	67.06
2005	66.31
2006	65.34
2007	64.35
2008	64.76
2009	67.39
2010	68.22
2011	68.88
2012	69.82
2013	69.45
2014	69.52
2015	69.86
2016	69.5
2017	69.18
2018	68.68
2019	67.81
2020	62.64