Year	Percent
1990	55.65
1991	56.94
1992	58.15
1993	59.27
1994	60.28
1995	59.59
1996	58.99
1997	58.34
1998	57.67
1999	57.02
2000	56.41
2001	56.16
2002	55.95
2003	55.73
2004	55.45
2005	55.05
2006	54.6
2007	54.07
2008	53.46
2009	52.81
2010	52.17
2011	51.7
2012	51.21
2013	50.63
2014	49.94
2015	49.14
2016	48.4
2017	47.64
2018	46.89
2019	46.86
2020	45.55