Year	Percent
1990	54.57
1991	54.5
1992	54.39
1993	52.3
1994	50.48
1995	49.44
1996	48.09
1997	47.23
1998	47.87
1999	48.75
2000	48.99
2001	48.75
2002	48.77
2003	49.62
2004	49.36
2005	50.15
2006	50.56
2007	50.36
2008	50.01
2009	49.98
2010	50.5
2011	50.76
2012	51.58
2013	52.07
2014	53.65
2015	54.83
2016	55.76
2017	56.25
2018	56.56
2019	56.82
2020	56.71