Year	Percent
1990	69.8
1991	71.21
1992	69.13
1993	68.81
1994	68.8
1995	68.3
1996	68.57
1997	69.3
1998	70.52
1999	70.86
2000	71.05
2001	71.78
2002	72.54
2003	72.75
2004	72.59
2005	73.24
2006	73.71
2007	73.97
2008	74.03
2009	73.43
2010	73.56
2011	73.55
2012	73.38
2013	73.05
2014	73.3
2015	73.6
2016	73.97
2017	74.91
2018	75.39
2019	75.77