Year	Percent
1990	68.87
1991	68.9
1992	68.91
1993	69.32
1994	69.26
1995	69.32
1996	69.44
1997	69.47
1998	69.46
1999	69.57
2000	69.67
2001	69.64
2002	69.65
2003	69.53
2004	69.11
2005	68.88
2006	68.99
2007	69.01
2008	69
2009	68.94
2010	68.7
2011	68.75
2012	68.61
2013	68.49
2014	68.32
2015	68.2
2016	68.28
2017	68.27
2018	68.12
2019	67.94