Year	Percent
1990	70.28
1991	71.05
1992	71.72
1993	72.28
1994	73.73
1995	74.81
1996	76.13
1997	76.77
1998	77.37
1999	77.81
2000	77.16
2001	77.89
2002	78.57
2003	79.7
2004	80.77
2005	81.8
2006	81.84
2007	81.44
2008	81.82
2009	81.08
2010	80.65
2011	79.93
2012	80.95
2013	81.27
2014	82.15
2015	81.18
2016	81.22
2017	81.21
2018	81.27
2019	81.34