Year	Percent
1990	52.2
1991	52.17
1992	52.15
1993	52.14
1994	52.13
1995	52.14
1996	52.12
1997	52.18
1998	52.25
1999	52.31
2000	52.36
2001	48.63
2002	48.65
2003	52.3
2004	52.27
2005	52.75
2006	52.51
2007	53.9
2008	52.92
2009	53.33
2010	54.23
2011	55.13
2012	54.85
2013	55.4
2014	55.55
2015	57.06
2016	57.03
2017	57.19
2018	56.55
2019	57.51