Year	Percent
1990	50.22
1991	51.45
1992	51.39
1993	53.12
1994	52.67
1995	52.23
1996	53.45
1997	54.33
1998	54.58
1999	54.58
2000	52.97
2001	53.52
2002	54.07
2003	54.11
2004	54.12
2005	54.66
2006	54.9
2007	54.31
2008	53.35
2009	52.73
2010	52.12
2011	51.64
2012	51.17
2013	50.68
2014	50.14
2015	49.51
2016	49.83
2017	50.07
2018	50.23
2019	50.32