Year	Percent
1990	59.79
1991	59.47
1992	58.35
1993	54.48
1994	56.98
1995	56.26
1996	55.77
1997	54.52
1998	54.55
1999	54.39
2000	51.51
2001	51.37
2002	51.26
2003	49.96
2004	49.18
2005	49.39
2006	48.49
2007	48.63
2008	49.42
2009	50.4
2010	51.61
2011	52.78
2012	52.81
2013	53.87
2014	54.6
2015	55.59
2016	56.56
2017	57.55
2018	58.08
2019	58.09