Year	Percent
1991	47.57
1992	47.59
1993	47.46
1994	47.42
1995	47.61
1996	47.94
1997	48.4
1998	48.85
1999	49.58
2000	50.3
2001	50.97
2002	51.54
2003	52.15
2004	52.88
2005	53.74
2006	54.71
2007	55.72
2008	56.69
2009	57.39
2010	58.2
2011	59.02
2012	59.78
2013	60.52
2014	59.87
2015	59.21
2016	58.42
2017	57.69
2018	56.95
2019	56.11