Year	Percent
1990	50.59
1991	50.86
1992	50.98
1993	50.87
1994	50.68
1995	50.36
1996	50.07
1997	49.91
1998	49.59
1999	49.58
2000	49.28
2001	49.05
2002	48.86
2003	48.71
2004	48.55
2005	48.43
2006	48.45
2007	48.52
2008	48.61
2009	48.51
2010	48.47
2011	48.44
2012	49.71
2013	49.71
2014	51.91
2015	52.86
2016	53.33
2017	53.34
2018	54.43
2019	55.52
2020	53.35