Year	Percent
1990	72.61
1991	73.79
1992	75.3
1993	74.98
1994	75.78
1995	73.73
1996	75.18
1997	75.94
1998	76.59
1999	78.17
2000	79.77
2001	79.76
2002	80.93
2003	80.38
2004	82.97
2005	83.94
2006	84.83
2007	84.92
2008	83.4
2009	84.75
2010	85.73
2011	85.65
2012	87.01
2013	87.52
2014	88.05
2015	87.76
2016	87.22
2017	88
2018	88.42
2019	88.52