Year	Percent
1991	76.9
1992	76.85
1993	76.76
1994	76.64
1995	76.52
1996	76.41
1997	76.36
1998	76.28
1999	76.15
2000	76.09
2001	76.07
2002	76.59
2003	77.11
2004	77.63
2005	78.15
2006	78.74
2007	79.24
2008	77.29
2009	75.07
2010	72.86
2011	73.06
2012	73.24
2013	73.41
2014	73.58
2015	73.61
2016	73.64
2017	73.66
2018	73.64
2019	73.59
2020	71.97