Year	Percent
1990	54.48
1991	54.68
1992	54.88
1993	55.13
1994	54.98
1995	54.77
1996	54.59
1997	54.06
1998	53.55
1999	53.07
2000	53.18
2001	53.29
2002	53.42
2003	53.81
2004	53.87
2005	53.93
2006	53.98
2007	54.45
2008	55.04
2009	55.4
2010	55.63
2011	55.47
2012	55.13
2013	55.75
2014	55.89
2015	55.52
2016	54.98
2017	55.16
2018	55.2
2019	55.48
2020	51.45