Year	Percent
1991	42.45
1992	42.5
1993	42.49
1994	42.47
1995	42.44
1996	42.38
1997	42.31
1998	42.24
1999	42.18
2000	42.19
2001	42.3
2002	42.41
2003	42.56
2004	42.73
2005	42.89
2006	42.85
2007	42.78
2008	42.66
2009	42.35
2010	42.2
2011	42.26
2012	42.35
2013	42.48
2014	42.67
2015	42.86
2016	43.03
2017	43.22
2018	43.38
2019	43.53
2020	41.54