Year	Percent
1991	47.2
1992	47.09
1993	46.9
1994	46.79
1995	46.73
1996	46.59
1997	46.44
1998	46.95
1999	47.37
2000	47.64
2001	47.88
2002	48.01
2003	48.21
2004	48.48
2005	48.79
2006	49.21
2007	49.6
2008	49.89
2009	49.76
2010	49.93
2011	50.31
2012	50.65
2013	50.96
2014	51.1
2015	51.16
2016	51.27
2017	51.45
2018	51.6
2019	51.7
2020	50.22