Year	Percent
1990	57.05
1991	56.86
1992	56.54
1993	56.12
1994	55.63
1995	55.12
1996	54.66
1997	54.24
1998	53.84
1999	53.43
2000	53
2001	52.7
2002	52.39
2003	52.12
2004	51.98
2005	52.02
2006	52.18
2007	52.5
2008	52.58
2009	53.7
2010	56.28
2011	57.65
2012	57.96
2013	58.21
2014	57.53
2015	56.86
2016	55.73
2017	55.43
2018	53.17
2019	52.93
2020	50.11