Year	Percent
1990	80.41
1991	81.02
1992	81.61
1993	82.23
1994	82.76
1995	83.25
1996	83.42
1997	83.58
1998	83.76
1999	83.95
2000	83.82
2001	83.72
2002	83.62
2003	83.54
2004	83.47
2005	83.41
2006	83.35
2007	83.31
2008	83.27
2009	83.23
2010	83.21
2011	83.19
2012	83.17
2013	83.17
2014	83.28
2015	83.4
2016	83.39
2017	83.51
2018	83.62
2019	83.69