Year	Percent
1990	64.96
1991	64.21
1992	63.46
1993	62.7
1994	61.95
1995	61.2
1996	60.44
1997	59.69
1998	58.94
1999	58.18
2000	57.43
2001	56.68
2002	55.92
2003	55.17
2004	54.42
2005	53.67
2006	52.91
2007	52.16
2008	51.41
2009	50.65
2010	49.9
2011	49.15
2012	48.39
2013	47.64
2014	46.89
2015	46.13