Year	Percent
1991	47.61
1992	46.9
1993	47.11
1994	48.23
1995	49.83
1996	50.69
1997	52.17
1998	55.45
1999	58.06
2000	59.83
2001	60.14
2002	59.95
2003	59.98
2004	60.24
2005	62.28
2006	62.95
2007	63.14
2008	61.37
2009	56.1
2010	53.8
2011	52.76
2012	52.46
2013	53.82
2014	54.81
2015	56
2016	57.17
2017	58.02
2018	58.78
2019	59.36
2020	57.75