Year	Percent
1991	69.25
1992	69.1
1993	68.84
1994	68.69
1995	68.61
1996	68.69
1997	68.77
1998	68.81
1999	68.76
2000	68.74
2001	69.23
2002	69.36
2003	69.41
2004	71.22
2005	72.41
2006	73.18
2007	73.84
2008	74.32
2009	74.42
2010	74.52
2011	76.48
2012	77.59
2013	76.33
2014	74.98
2015	73.5
2016	73.01
2017	72.61
2018	72.23
2019	71.83