Year	Percent
1991	52.43
1992	52.67
1993	52.94
1994	53.06
1995	53.13
1996	53.22
1997	53.07
1998	52.81
1999	52.48
2000	52.06
2001	51.63
2002	51.22
2003	50.84
2004	50.48
2005	50.18
2006	49.93
2007	49.76
2008	49.83
2009	50.03
2010	50.02
2011	49.99
2012	49.91
2013	49.69
2014	49.36
2015	48.99
2016	48.59
2017	48.17
2018	47.74
2019	47.34
2020	45.71