Year	Percent
1991	43.96
1992	43.91
1993	43.81
1994	43.86
1995	43.78
1996	43.6
1997	43.45
1998	43.26
1999	43.06
2000	42.92
2001	42.71
2002	42.5
2003	42.37
2004	42.28
2005	42.22
2006	42.11
2007	41.98
2008	41.82
2009	41.47
2010	41.31
2011	41.16
2012	41.07
2013	41.01
2014	41.03
2015	41.07
2016	41.16
2017	41.31
2018	41.47
2019	41.63
2020	41.28