Year	Percent
1991	78.4
1992	78.65
1993	78.96
1994	80.18
1995	79.99
1996	79.72
1997	79.64
1998	79.4
1999	79.18
2000	77.96
2001	82.61
2002	81.87
2003	80.89
2004	79.53
2005	79.92
2006	80.37
2007	80.75
2008	81.5
2009	82.08
2010	84.57
2011	85.37
2012	83.03
2013	80.41
2014	80.1
2015	80.01
2016	81.77
2017	82.14
2018	82.05
2019	81.94
2020	79.11