Year	Percent
1991	58.62
1992	56.85
1993	50.9
1994	49.31
1995	48.89
1996	47.53
1997	51.01
1998	50.32
1999	49.6
2000	48.09
2001	48.55
2002	49.81
2003	50.09
2004	50.55
2005	51.52
2006	54.86
2007	56.56
2008	56.73
2009	49.57
2010	47.49
2011	49.11
2012	50.76
2013	52.31
2014	52.81
2015	54.13
2016	54.77
2017	55.88
2018	57.2
2019	57.54
2020	56.77