Year	Percent
1990	61.8
1991	62.27
1992	62.95
1993	63.36
1994	63.39
1995	65.34
1996	73.62
1997	72.79
1998	72.14
1999	71.78
2000	71.35
2001	71.84
2002	69.48
2003	67.56
2004	68.4
2005	69.54
2006	71.32
2007	73.97
2008	75.09
2009	75.56
2010	75.86
2011	76.37
2012	76.31
2013	76.57
2014	77.69
2015	77.83
2016	77.44
2017	77.62
2018	78.17
2019	78.15