Year	Percent
1990	60.28
1991	60.55
1992	60.76
1993	61.02
1994	61.19
1995	60.9
1996	61.16
1997	61.62
1998	61.9
1999	61.8
2000	61.85
2001	61.7
2002	61.14
2003	61.71
2004	62.29
2005	61.95
2006	62.23
2007	61.47
2008	60.71
2009	61.06
2010	60.4
2011	60.63
2012	60.5
2013	60.22
2014	59.69
2015	60.02
2016	60.31
2017	60.59
2018	61.39
2019	61.61
2020	55.97