Year	Percent
1991	60.31
1992	57.09
1993	54.16
1994	53.78
1995	53.66
1996	54.81
1997	55.86
1998	56.22
1999	55.48
2000	55.88
2001	55.38
2002	55.43
2003	54.11
2004	54.91
2005	54.24
2006	53.62
2007	52.69
2008	52.14
2009	48.09
2010	47.06
2011	45.81
2012	46.1
2013	46.05
2014	47.76
2015	49.75
2016	50.45
2017	50.27
2018	50.34
2019	50.11