Year	Percent
1991	40.28
1992	40.24
1993	40.47
1994	40.85
1995	41.29
1996	41.18
1997	41.44
1998	41.63
1999	42
2000	42.37
2001	42.78
2002	43.16
2003	43.52
2004	43.66
2005	43.63
2006	43.53
2007	43.39
2008	43.74
2009	43.85
2010	43.57
2011	43.71
2012	43.78
2013	43.76
2014	43.78
2015	43.84
2016	43.92
2017	44.01
2018	44.22
2019	44.63
2020	42.32