Year	Percent
1991	58.52
1992	58.13
1993	57.89
1994	58.73
1995	59.14
1996	61.15
1997	62.8
1998	64.39
1999	64.48
2000	64.61
2001	64.39
2002	64.4
2003	63.03
2004	62.93
2005	62.56
2006	63.45
2007	64.74
2008	65.7
2009	64.38
2010	63.38
2011	63.11
2012	63.26
2013	62.77
2014	62.46
2015	62.1
2016	61.36
2017	60.95
2018	61.5
2019	61.71
2020	60.79