Year	Percent
1990	75.88
1991	75.8
1992	75.86
1993	74.06
1994	71.97
1995	71.39
1996	70.15
1997	68.41
1998	67.19
1999	70.86
2000	70.96
2001	69.66
2002	70.61
2003	70.49
2004	71.13
2005	71.57
2006	71.86
2007	72.7
2008	73
2009	72.85
2010	72.73
2011	73.06
2012	73.16
2013	73.19
2014	73.43
2015	73.68
2016	74.24
2017	74.15
2018	74.43
2019	73.96