Year	Percent
1991	62.76
1992	62.47
1993	60.26
1994	56.99
1995	55.62
1996	54.51
1997	51.95
1998	50.31
1999	53.18
2000	54.7
2001	54.52
2002	55.69
2003	55.18
2004	55.81
2005	56.56
2006	56.85
2007	58.28
2008	58.57
2009	57.29
2010	57.84
2011	58.59
2012	59.29
2013	59.17
2014	59.39
2015	59.14
2016	59.28
2017	59.08
2018	59.23
2019	58.66
2020	57.62