Year	Percent
1990	68.11
1991	67.06
1992	66
1993	64.95
1994	63.9
1995	62.84
1996	61.79
1997	60.74
1998	59.68
1999	58.63
2000	57.58
2001	56.53
2002	55.47
2003	54.42
2004	53.37
2005	52.31
2006	51.26
2007	50.21
2008	49.16
2009	48.11
2010	47.06
2011	46
2012	44.95
2013	43.89
2014	42.84
2015	41.78