Year	Percent
1990	72.72
1991	72.84
1992	74
1993	75.07
1994	76.08
1995	76.8
1996	78.12
1997	79.38
1998	80.02
1999	81.4
2000	79.62
2001	83.05
2002	83.41
2003	83.05
2004	84.47
2005	82.39
2006	85.61
2007	87.84
2008	87.4
2009	87.69
2010	88.06
2011	88.1
2012	88.06
2013	88.02
2014	86.92
2015	86.41
2016	86.11
2017	87.55
2018	87.88
2019	87.45