Year	Percent
1990	55.43
1991	55.3
1992	55.19
1993	55.05
1994	54.89
1995	54.59
1996	54.43
1997	54.2
1998	53.87
1999	53.53
2000	53.27
2001	53.11
2002	53.03
2003	52.86
2004	52.71
2005	52.59
2006	52.6
2007	52
2008	51.39
2009	50.78
2010	50.15
2011	49.55
2012	48.95
2013	48.34
2014	47.72
2015	47.11
2016	47.13
2017	47.13
2018	47.13
2019	47.14