Year	Percent
1990	42.95
1991	42.97
1992	43.06
1993	43.21
1994	43.4
1995	43.63
1996	43.73
1997	43.9
1998	44.13
1999	44.41
2000	44.74
2001	45.03
2002	45.39
2003	45.8
2004	46.25
2005	46.74
2006	47.12
2007	47.5
2008	47.85
2009	48.21
2010	48.56
2011	48.86
2012	49.11
2013	49.32
2014	49.45
2015	49.51
2016	49.63
2017	49.7
2018	49.73
2019	49.7
2020	48.15