Year	Percent
1990	42.81
1991	42.99
1992	42.91
1993	42.91
1994	43.04
1995	42.98
1996	42.99
1997	42.89
1998	42.82
1999	42.75
2000	42.53
2001	42.47
2002	42.42
2003	42.39
2004	42.39
2005	42.65
2006	42.95
2007	43.27
2008	43.63
2009	44.01
2010	44.4
2011	44.8
2012	45.21
2013	45.62
2014	46.02
2015	46.19
2016	46.3
2017	46.39
2018	46.47
2019	46.56