Year	Percent
1990	70.09
1991	71.29
1992	72.6
1993	73.9
1994	74.98
1995	75.7
1996	75.15
1997	74.3
1998	73.35
1999	72.48
2000	71.68
2001	71.44
2002	71.45
2003	71.64
2004	71.95
2005	72.32
2006	72.69
2007	73.3
2008	74.15
2009	75.23
2010	76.45
2011	77.66
2012	78.95
2013	80.18
2014	81.24
2015	82.09
2016	82.4
2017	81.89
2018	79.73
2019	79.83