Year	Percent
1989	41.53
1990	41.77
1991	43.7
1992	45.92
1993	50.78
1994	53.35
1995	55.59
1996	56.63
1997	56.84
1998	57.75
1999	59.78
2000	58.65
2001	59.9
2002	63.6
2003	63.06
2004	60.98
2005	60.69
2006	61.36
2007	60.04
2008	60.72
2009	64.4
2010	65.37
2011	63.11
2012	64.35
2013	65.4
2014	65.91
2015	65.3
2016	66.21
2017	66.24