Year	Percent
1990	77.4
1991	77.7
1992	80
1993	82.6
1994	84.64
1995	85.51
1996	85.4
1997	84.94
1998	84.17
1999	83.58
2000	82.76
2001	80.85
2002	79.03
2003	77.09
2004	75.53
2005	74.08
2006	72.61
2007	71.62
2008	70.19
2009	69.89
2010	69.36
2011	68.69
2012	68.96
2013	69.29
2014	69.9
2015	70.3
2016	71.2
2017	71.71
2018	72.16
2019	72.04