Year	Percent
1991	56.23
1992	57.42
1993	58.5
1994	59.33
1995	58.47
1996	57.69
1997	56.86
1998	55.99
1999	55.12
2000	54.3
2001	53.82
2002	53.33
2003	52.84
2004	53.52
2005	53.88
2006	54.01
2007	53.43
2008	52.76
2009	51.99
2010	51.26
2011	50.71
2012	50.13
2013	49.46
2014	48.71
2015	47.84
2016	47.04
2017	46.25
2018	45.45
2019	45.45
2020	43.56