Year	Percent
1990	80.11
1991	80.1
1992	80.05
1993	79.92
1994	79.86
1995	79.75
1996	79.67
1997	79.6
1998	79.55
1999	79.49
2000	79.44
2001	79.56
2002	79.66
2003	79.74
2004	79.79
2005	79.83
2006	79.34
2007	78.84
2008	78.31
2009	77.76
2010	77.18
2011	76.63
2012	76.07
2013	76.01
2014	75.92
2015	75.8
2016	75.67
2017	75.5
2018	75.3
2019	75.13