Year	Percent
1991	51.11
1992	51.63
1993	50.91
1994	50.27
1995	48.82
1996	49.14
1997	49.72
1998	49.78
1999	50.82
2000	52.12
2001	51.87
2002	52.45
2003	51.19
2004	51.33
2005	52.34
2006	52.66
2007	52.78
2008	52.23
2009	54.34
2010	54.5
2011	54.07
2012	55.03
2013	54.88
2014	55.57
2015	55.4
2016	54.51
2017	55.43
2018	55.89
2019	56.57
2020	55.8