Year	Percent
1991	60.23
1992	60.19
1993	60.1
1994	60.07
1995	60.1
1996	60.09
1997	60.15
1998	60.23
1999	60.29
2000	60.36
2001	60.49
2002	60.61
2003	60.73
2004	60.78
2005	60.57
2006	60.4
2007	60.21
2008	59.97
2009	59.59
2010	59.31
2011	59.36
2012	64.23
2013	59.4
2014	60.1
2015	59.89
2016	60.34
2017	60.67
2018	60.92
2019	61.16
2020	54.4