Year	Percent
1991	68.72
1992	67.78
1993	67.75
1994	67.21
1995	66.75
1996	67
1997	67.6
1998	67.78
1999	68.14
2000	70.15
2001	71.29
2002	71.74
2003	71.31
2004	71.05
2005	70.76
2006	70.4
2007	69.97
2008	69.47
2009	69.99
2010	69.94
2011	69.23
2012	69.38
2013	69.68
2014	69.76
2015	69.81
2016	69.8
2017	69.75
2018	69.67
2019	69.71