Year	Percent
1990	74.07
1991	73.91
1992	74.23
1993	74.59
1994	74.63
1995	74.97
1996	75.11
1997	75.38
1998	75.61
1999	75.63
2000	74.76
2001	73.79
2002	73.69
2003	73.58
2004	73.46
2005	73.33
2006	72.13
2007	71.37
2008	71.8
2009	72.6
2010	74.57
2011	71.97
2012	71.39
2013	74.83
2014	77.07
2015	76.58
2016	76.82
2017	76.19
2018	78.27
2019	78.59