Year	Percent
1991	57.36
1992	55.78
1993	55.8
1994	58.6
1995	60.78
1996	60.62
1997	59.15
1998	59.89
1999	60.78
2000	61.66
2001	61.06
2002	60.9
2003	61.73
2004	62.14
2005	63.29
2006	63.7
2007	64.15
2008	64.54
2009	61.21
2010	60.62
2011	60.44
2012	59.61
2013	58.65
2014	57.7
2015	58.44
2016	58.25
2017	58.23
2018	59.48
2019	59.63