Year	Percent
1991	61.26
1992	61.21
1993	53.68
1994	53.89
1995	51.31
1996	51.67
1997	52.65
1998	52.54
1999	52.93
2000	50.55
2001	48.84
2002	50.61
2003	52.41
2004	51.03
2005	51.51
2006	52.04
2007	53.21
2008	52.65
2009	48.85
2010	46.82
2011	48.95
2012	50.38
2013	51.42
2014	52.79
2015	53.86
2016	55.79
2017	56.6
2018	57.96
2019	58.11
2020	56.8