Year	Percent
1991	52.7
1992	53.38
1993	54.09
1994	54.55
1995	54.79
1996	54.87
1997	55.16
1998	55.51
1999	55.73
2000	55.81
2001	55.78
2002	55.74
2003	55.61
2004	55.48
2005	55.48
2006	55.56
2007	55.78
2008	56.24
2009	56.88
2010	56.76
2011	56.29
2012	55.84
2013	55.34
2014	54.84
2015	54.48
2016	54.14
2017	53.88
2018	53.65
2019	53.43
2020	52.08