Year	Percent
1992	59.43
1993	59.66
1994	59.88
1995	60.1
1996	60.33
1997	60.55
1998	60.77
1999	61
2000	61.22
2001	61.32
2002	61.42
2003	61.52
2004	61.62
2005	61.72
2006	61.76
2007	61.8
2008	61.84
2009	61.88
2010	61.92
2011	61.93
2012	61.94
2013	61.95
2014	61.96
2015	61.97