Year	Percent
1991	56.75
1992	56.76
1993	56.66
1994	56.43
1995	56.02
1996	56.02
1997	55.79
1998	55.44
1999	55
2000	54.63
2001	54.27
2002	53.86
2003	53.46
2004	53.03
2005	52.58
2006	52.39
2007	52.14
2008	51.83
2009	51.35
2010	51.05
2011	50.97
2012	50.87
2013	50.74
2014	50.61
2015	50.42
2016	50.3
2017	50.13
2018	49.89
2019	49.55