Year	Percent
1991	55.15
1992	55.09
1993	55.03
1994	55.03
1995	54.91
1996	54.77
1997	54.63
1998	54.49
1999	54.34
2000	54.23
2001	54.34
2002	54.43
2003	54.55
2004	54.71
2005	54.89
2006	54.17
2007	53.46
2008	52.74
2009	51.88
2010	51.15
2011	50.28
2012	49.44
2013	48.96
2014	48.52
2015	48.08
2016	47.64
2017	47.21
2018	46.79
2019	46.74
2020	43