Year	Percent
1990	55.52
1991	55.06
1992	55.16
1993	55.15
1994	55.07
1995	55.1
1996	55.5
1997	55.16
1998	55.21
1999	55.45
2000	55.39
2001	55.08
2002	55.29
2003	55.94
2004	55.82
2005	55.9
2006	55.8
2007	55.93
2008	56.03
2009	56.21
2010	56.11
2011	55.85
2012	56.02
2013	55.99
2014	55.59
2015	55.5
2016	55.4
2017	55.27
2018	55.29
2019	54.97
2020	54.12