Year	Percent
1991	50.57
1992	50.43
1993	50.25
1994	50.09
1995	49.8
1996	49.65
1997	49.43
1998	49.12
1999	48.79
2000	48.56
2001	48.42
2002	48.33
2003	47.63
2004	46.95
2005	46.26
2006	45.7
2007	45.27
2008	44.78
2009	44.07
2010	43.5
2011	42.99
2012	42.93
2013	42.83
2014	42.73
2015	42.58
2016	42.62
2017	42.65
2018	42.68
2019	42.7
2020	41.12