Year	Percent
1990	50.3
1991	50.33
1992	50.37
1993	50.43
1994	50.49
1995	50.55
1996	50.66
1997	50.78
1998	51.09
1999	51.38
2000	51.66
2001	51.91
2002	52.14
2003	52.37
2004	52.6
2005	52.85
2006	53.1
2007	53.38
2008	53.57
2009	53.73
2010	53.88
2011	54.03
2012	54.15
2013	55.23
2014	56.3
2015	56.66
2016	56.98
2017	55.43
2018	55.59
2019	55.68