Year	Percent
1990	51.34
1991	51.38
1992	51.17
1993	50.95
1994	50.71
1995	50.45
1996	50.26
1997	50.06
1998	49.84
1999	49.6
2000	49.35
2001	49.21
2002	49.06
2003	48.9
2004	48.73
2005	48.54
2006	48.47
2007	48.39
2008	48.29
2009	48.19
2010	48.08
2011	48.02
2012	47.94
2013	47.82
2014	47.64
2015	47.44
2016	47.24
2017	47.03
2018	46.73
2019	46.39