Year	Percent
1990	75.25
1991	76.24
1992	77.23
1993	78.17
1994	79
1995	79.17
1996	79.27
1997	79.32
1998	79.34
1999	79.38
2000	79.41
2001	79.64
2002	79.84
2003	79.91
2004	79.89
2005	79.85
2006	80.05
2007	80.21
2008	80.28
2009	80.28
2010	80.3
2011	80.33
2012	80.45
2013	80.61
2014	80.79
2015	80.95
2016	81.1
2017	81.22
2018	81.34
2019	81.46