Year	Percent
1991	52.96
1992	52.97
1993	52.89
1994	52.06
1995	51.42
1996	50.87
1997	51.93
1998	51.38
1999	52.72
2000	54.44
2001	56.03
2002	55.95
2003	56.27
2004	56.61
2005	56.94
2006	57.84
2007	58.3
2008	58.39
2009	58.1
2010	57.96
2011	57.97
2012	57.99
2013	58.02
2014	58.56
2015	59.16
2016	60.48
2017	60.56
2018	60.81
2019	61.02
2020	56.55