Year	Percent
1991	67.91
1992	67.95
1993	68.02
1994	68.07
1995	68.03
1996	67.74
1997	67.52
1998	67.41
1999	68.95
2000	68.09
2001	67.41
2002	67.69
2003	67.77
2004	67.72
2005	67.52
2006	67.64
2007	67.08
2008	66.41
2009	65.69
2010	65.11
2011	64.69
2012	64.3
2013	64.14
2014	63.92
2015	63.76
2016	63.59
2017	63.99
2018	64.26
2019	64.34
2020	63.86