Year	Percent
1991	56.76
1992	57.7
1993	58.6
1994	58.93
1995	59.97
1996	60.01
1997	60.05
1998	60.17
1999	60.24
2000	60.55
2001	60.86
2002	61.12
2003	61.39
2004	61.85
2005	62.15
2006	61.37
2007	61.95
2008	63.48
2009	62.34
2010	61.16
2011	60.86
2012	62.65
2013	63.59
2014	62.9
2015	62.94
2016	63.21
2017	62.39
2018	64.03
2019	64.11
2020	56.21