Year	Percent
1990	61.2
1991	61.11
1992	60.92
1993	60.83
1994	60.73
1995	60.6
1996	60.46
1997	60.34
1998	60.24
1999	60.19
2000	60.09
2001	60.06
2002	59.87
2003	59.84
2004	59.78
2005	59.79
2006	59.85
2007	59.9
2008	59.94
2009	59.93
2010	59.91
2011	59.95
2012	57.52
2013	55.1
2014	54.55
2015	53.91
2016	53.19
2017	54.14
2018	55.04
2019	55.87
2020	53.43