Year	Percent
1991	56.59
1992	56.96
1993	58.02
1994	58.45
1995	58.21
1996	55.99
1997	52.21
1998	49.58
1999	48.05
2000	46.98
2001	49.31
2002	50.93
2003	52.44
2004	52.89
2005	53.92
2006	57
2007	60.58
2008	63.88
2009	66.84
2010	69.12
2011	66.07
2012	64.58
2013	64.75
2014	65.94
2015	67.56
2016	65.7
2017	64.2
2018	63.67
2019	63.38