Year	Percent
1990	58.99
1991	59.87
1992	60.23
1993	60.04
1994	59.69
1995	59.06
1996	58.42
1997	57.77
1998	57.43
1999	58.06
2000	57.46
2001	56.84
2002	56.29
2003	55.86
2004	55.25
2005	54.85
2006	54.48
2007	54.42
2008	53.6
2009	52.05
2010	50.84
2011	50.81
2012	51.23
2013	52.06
2014	52.36
2015	52.06
2016	53.82
2017	54.47
2018	55.07
2019	55.24
2020	54.17