Year	Percent
1990	54.71
1991	55.21
1992	55.6
1993	56.02
1994	56.39
1995	56.71
1996	56.65
1997	56.58
1998	56.51
1999	56.43
2000	56.34
2001	55.9
2002	55.79
2003	54.68
2004	54.44
2005	54.15
2006	53.99
2007	55.85
2008	55.45
2009	56.29
2010	55.88
2011	55.45
2012	54.56
2013	53.89
2014	53.86
2015	53.88
2016	53.94
2017	54.02
2018	54.13
2019	54.26