Year	Percent
1990	60.01
1991	59.34
1992	58.68
1993	58.01
1994	57.35
1995	56.68
1996	56.01
1997	55.35
1998	54.68
1999	54.02
2000	53.35
2001	52.88
2002	52.41
2003	51.93
2004	51.47
2005	51
2006	50.52
2007	50.04
2008	49.58
2009	49.11
2010	48.64
2011	47.8
2012	46.97
2013	46.14
2014	45.3
2015	44.47