Year	Percent
1990	80.29
1991	80.36
1992	80.37
1993	80.37
1994	80.33
1995	80.27
1996	80.34
1997	80.38
1998	80.37
1999	80.44
2000	80.53
2001	80.61
2002	80.69
2003	80.78
2004	80.88
2005	80.93
2006	80.99
2007	81.03
2008	81.02
2009	81.03
2010	80.99
2011	81
2012	78.88
2013	76.5
2014	73.85
2015	73.76
2016	73.68
2017	73.6
2018	73.49
2019	73.39