Year	Percent
1991	69.66
1992	67.68
1993	68.09
1994	64.25
1995	62.78
1996	64.7
1997	62.83
1998	63.77
1999	65.08
2000	65.01
2001	63.9
2002	65.31
2003	63.42
2004	61.91
2005	59.92
2006	63.47
2007	62.8
2008	62.65
2009	61.63
2010	62.4
2011	63.17
2012	61.88
2013	62.05
2014	62.14
2015	61.73
2016	62.62
2017	63.25
2018	62.71
2019	61.17