Year	Percent
1991	58.12
1992	58.49
1993	59.14
1994	59.4
1995	59.68
1996	57.88
1997	57.93
1998	57.32
1999	57.34
2000	57.75
2001	58.15
2002	58.94
2003	58.55
2004	59.75
2005	60.02
2006	60.27
2007	60.18
2008	60.82
2009	60.24
2010	59.73
2011	59.19
2012	59.67
2013	59.7
2014	59.64
2015	58.65
2016	56.39
2017	55.84
2018	56.15
2019	56.76
2020	51.14