Year	Percent
1991	57.65
1992	57.07
1993	55.98
1994	55.42
1995	55.32
1996	55.31
1997	53.91
1998	54.14
1999	53.62
2000	52.8
2001	53.25
2002	50.74
2003	49.67
2004	45.51
2005	44.78
2006	44.94
2007	47.04
2008	47
2009	44.36
2010	44.36
2011	45.18
2012	44.47
2013	46.33
2014	46.35
2015	45.35
2016	45.74
2017	46.46
2018	49.56
2019	49.17