Year	Percent
1991	49.3
1992	49.37
1993	49.26
1994	48.92
1995	48.45
1996	47.63
1997	47.01
1998	46.62
1999	46.57
2000	47.57
2001	47.16
2002	46.79
2003	46.96
2004	47.2
2005	47.44
2006	47.39
2007	47.65
2008	47.86
2009	47.58
2010	48.42
2011	49.39
2012	50.78
2013	51.62
2014	52.03
2015	52.91
2016	53.14
2017	52.65
2018	52.15
2019	52.45
2020	50.61