Year	Percent
1990	69.85
1991	70.59
1992	71.37
1993	72.15
1994	72.95
1995	72.32
1996	71.08
1997	69.91
1998	69.42
1999	68.98
2000	66.19
2001	68.95
2002	67.13
2003	68.88
2004	67.73
2005	67.8
2006	68.57
2007	69.32
2008	70.05
2009	70.74
2010	72.61
2011	73.66
2012	74.31
2013	73.74
2014	74.57
2015	75.43
2016	74.25
2017	72.73
2018	70.3
2019	69.4