Year	Percent
1990	68.67
1991	68.69
1992	68.86
1993	69.02
1994	69.07
1995	69
1996	68.4
1997	67.81
1998	67.29
1999	66.9
2000	67.23
2001	67.01
2002	67.04
2003	67.36
2004	67.68
2005	67.98
2006	68.05
2007	68.46
2008	68.55
2009	68.43
2010	68.88
2011	69.21
2012	69.95
2013	70.18
2014	70.12
2015	70.79
2016	70.9
2017	70.31
2018	69.6
2019	69.73