Year	Percent
1991	57.81
1992	58.17
1993	56.84
1994	55.68
1995	54.12
1996	53.33
1997	54.49
1998	53.76
1999	52.66
2000	52.09
2001	51.18
2002	50.5
2003	49.64
2004	48.82
2005	48.04
2006	47.43
2007	46.88
2008	47.86
2009	47.07
2010	46.63
2011	52.02
2012	49.43
2013	44.69
2014	43.68
2015	46.05
2016	47.89
2017	49.32
2018	52.03
2019	53.41
2020	52.73